In my own experience, only at first. I started printing anything willy nilly, just to try it out. Then when I felt like I just had too much stuff, I became more selective with what I print. I keep all the discarded parts, objects, and failed prints in a box, since I'll be able to re-melt and reuse the plastic eventually.
I'm not really worried about printing useless items, I'm more concerned that the 3-d printer itself is one more (fairly significant) item of "stuff" to have to deal with. For a 3-d printer purchase to result in a net-negative amount of stuff, it would need to allow me to get rid of a lot of other stuff in my life.
If 3-d printers eventually reach the stage where I can print an item only when I need it, and then I can recycle it into something else, that would be worth owning. Looking around my kitchen, I see a lot of things that I don't use every week, but I use enough (and are useful enough) that they're worth keeping around: a gravy separator, multiple salad bowls, a ladle, a colander, steamer baskets, multiple slotted spoons, multiple potholders, storage containers, various sizes of bakeware, enough placesettings to have guests, etc. I can imagine 3-d printers eventually getting to the point where there's no reason to keep drawers and cabinets full of this stuff. But with today's technology, if you're printing something that you need to use today a month from now, you're generally better off throwing the one you have on a shelf for a month than printing a new one the next time you need it. When that changes, I'll be more interested.
