I recently read a story in The Year's Best SF 12 ('06, of course, but published this year) called Nano comes to Clifton Falls, written by Nancy Kress. I've never much liked her stories, and this is just bad SF. (She can write and tell a story well. It's her ideas and how she works them that are questionable.) It starts out with nano fab devices being delivered all across the country, and they've been delivered to Clifton Falls (somewhere in the mid-west I think). Everything - food or object - is made by a kind of fabber, and so people don't have to work anymore. Not quite, because they still have to fix things, and so the country swiftly goes to pot.
Um, well no. These kinds of things don't happen all by themselves. Usually there are parallel (not to mention gradual) developments - like automated repair or self-maintaining structures, etc. Here, Kress pulls a 50's 'what if this happened?' and just lets it run unchecked.
Then of course there's the fact that everyone seems to be getting theirs around the same time. Not to mention that that kind of pulls the shine off the title - you know, them bumpkins is getting new-fangled stuff finally, hey! - but that it isn't likely. Cities would have them first, and their 'falls' would likely happen before the little places got theirs, especially with how quick it happened.
However, there's something that precludes all this: what feeds the fabbers?? Apparently it's plentiful, right? How??
These are all questions a serious reader doesn't even have to ask. They're just evident.