I've always heard that 300 dpi is the optimum print resolution. However, images from my 6 MP camera are not large enough for even an 8x10 at 300 dpi, much less something like an 11x17. Recently however, I read a post on this site saying that print resolution should usually be between 240 and 300 dpi. Is 240 going to be distinguishable from 300 in most cases? What is the lowest resolution you would try to get away with?
Also, why is "ppi" used increasingly instead of "dpi"?