Getting worried 

I wonder how much the "ink" catridges for a 3-D printer costs.

I'll bet $1M that they'll follow HPs example, and will use the "Gillette Model"

http://www.investopedia.com/ask/answers/08/razor-blade-model.asp

In any case, it's a Prepper's dream, because now they can make their own guns.

No, it isn't.  If someone even so much as thinks about making their own firearms receivers with 3d printing, the BATF is going to be kicking their doors down SWAT-style and throwing the book at them afterwards.  And the book of firearms laws is extremely large and heavy.

Unless someone tries to mass produce them for sale, the gov't would never know.

Yes, it is. It's damn near impossible, not to mention a bad idea, to police what people do in their own homes. Once good 3d printers become viable for consumers, a whole new world is going to open up. And with the internet around it's not like you censor designs either. Not that i see a problem with people wanting to print guns, even in a onetime use design some parts will still have to be metal, and if you have bad intentions you can get a weapon by other means. And we're still a ways off from printable ammunition.

But for the near future i can imagine 3d print shops maybe becoming a thing, especially once someone makes a tool to make designs the average joe can use. I don't see a printer good/big enough to print everyday household objects being available for individuals anytime soon. 

If you don't want to wait for prices to drop or you like building things:

http://news.filehippo.com/2014/06/build-3d-printer-100/

You can obtain files for 3D printing of anything(almost anything). You can obtain the files to create your own gun, it would not be difficult if you know where to look. Thing is, is it illegal to own a 3D printed gun? Are there laws in place for that?

This is the future. The industries should be taking note of all the things I could now print myself. If I wanted to, because the cost of a spool is cheap($26-PLA spool on Monoprice). Guns, Ammo, Cups, Screws, Frames, Phone Cases, Computer Mice, etc. If I can model it, I can create it. If someone else can model it and share their file, I can create it.

It's great for the do it yourselfer, and even better for consumers. I can't wait to get myself a 3D printer.

But how long until medium sized stuff like chairs or lamps (in several parts)? And how long until it is cheaper them mass production?

I think there's a cost vs size ratio that will happen at some point EleventhStar, where the DIYer can't produce a chair for how much Target can produce it. Cost of a spool is around $26+/- for PLA(Costs vary between ABS, PLA and then proprietary spools). Chairs cost about $20-$30 and you would spend more on spools than you'd get out of them.

But in the DIY market, fairs and conventions, a $26 spool becomes worth a lot more once you've printed it into something. What you print with it is up to you and if you can model, you stand to make some quick cash online. Just have to be careful of copyrights and trademarks. Just because you can make something with a 3D printer, doesn't mean you're free from the law. But you'll see "parody" pieces that are almost the exact same whatever.

I just enjoy knowing if I broke a piece of my camera, or keyboard, or mouse, I could model it, print it, replace it. And what makes this easier is 3D scanning tools...But that's a whole other topic.

Im excited!

If you are talking the US, I'd guess that the answer is no, as long as it is not automatic, or doesn't violate any barrel length laws (i.e. short shot-guns). I'm only guessing that because you are legally allowed to make your own guns (ignoring buying separate parts and assembling as that is something different) as long as they are for yourself.

Of course being a machinist and not a lawyer, these are all just guesses, I'd not recommend someone using my post as their legal basis.

What annoys, and scares me about new technology are the people who will use it for undesirable reasons... eg, using 3D printers to make guns and/or other weapons to inflict harm or death on others.

If it were up to me, I'd have some software mechanism in ALL 3D printers that prevented users making guns, knives and other offensive weapons that kill and maim.

The fact that gun creation was even mentioned is a worry... cos if one sane and sensible person can think of it, there'll be a whole raft of effwits who'll put the thought into practice to wreak havoc on society.

In the U.S., the NRA would make sure that it was legal to print your own guns. Because owning a gun is a God given right after all.

There's NO such thing as a God given right.... and the 1000's upon 1000's of senseless tragedies where innocents are maimed or killed by firearms should serve as a more than logical reason to crush ALL guns in civilian hands.  I mean, let's face it, firearms in the US are used more frequently to recklessly and senselessly kill or maim others than they are for self defense.  It makes absolutely no sense to fight for a system that allows such things to happen almost hourly every day of every year.  For mine it is madness and uncivilised... because senseless killing is uncivilised.

Anyway, getting back to the topic at hand, I hope that 3D printing will bring about a new and innovative field of medical research and application... to be able to repair body parts where it was simply not possible before.  I'd also like to see consumers armed with the ability to manufacture parts to repair devices which have in-built obsolescence through components [criminally] that have 'sooner than should be' use by dates. 

For example, I have a 32" LCD TV that is perfectly okay but for the starter component board, which died about 3 weeks after the warranty expired.  To have that [$25 wholesale] board replaced, I was quoted beteween $250 - $300 for parts and labour.  Like heck, I replaced it with a brand new 40" LCD/LED TV with more features for just $329. 

However, had I been in possession of a 3D printer capable of printing that circuit board [among other things] I'd have saved myself 300 bucks.  Similarly, my niece recently had her phone die just a few days out of warranty, and the cost to repair it is ridiculously more than the cost of purchasing a new phone... again with more and better features than her previous one.

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Oh, and about my previous comment regarding "sane and sensible people", I hope you didn't think I was directing it at you.  My apologies if you did... cos anyone who posts a thread with a test for psychpathic tendencies, and scores relatively well, obviously doesn't belong in that category.  Honestly, I don't know what came over me, but something must have because I normally strive so as not to insult or offend people... attribute characteristics to them that they obviously do not possess.  Worse still, I've offended The Collective, so again, please accept my apology and do not tell 2of3 of my errant ways.

Your right and this is why all 3d printers should have massive intrusive DRM that ruthlessly enforces patent and copyright law to prevent people from stealing others ideas and harming the owners of those ideas. Use or ownership of a non-regulated 3d printer should be punishable with jail time and hefty fines.

Of course anyone with a basic machine shop can make much much better guns in their garage unsupervised then you will be able to make with a 3d printer for at least a decade or 2 but that only proves that we need a new agency to enforce government regulation in everyones homes and constantly monitor and control every garage or workshop where potentially dangerous things could in theory be produced.

*End Sarcasm.

Yes I know. That's why I put a "rolling eyes" smiley after the comment. It was meant as a "tongue in check" remark.