sometimes a fake boob is better than no-boob or really uneven-boobs.
most of the time, boobs aren't the same size, but it's not easy to notice. sometimes it can be a lot. an X of mine had a small b and a large c. she couldnt' wear anything with stripes of you could really notice. just plain colored tops. when she got a boob job, she went to a full D, as filling the small one just to match would mean they wouldnt' hang even at all for years. you could still tell after the boob job for a few months, then it got really hard to notice.
still, nice real boobs are the best. but when you don't ahve the best, might as well go plastic.
my x also got it done via the belly button. they use a tube to stick an empty bag into the boob, then fill it up. was freaky to watch on video.
and man, nothing sadder than a fat chick w/o boobs. that's supposed to be the consolation prize for getting fat, free tits. but when that doesn't happen, man you just feel bad.