My best friend at Uni had breast implants put in about 7 years ago. When they were first in, they looked good, but they look awful now. First she lost quite a few pounds, which left her with less fatty tissue on her breasts, and left you able to see ridges at the edge of the implants. Then she had a baby, which meant they got enormous and shrunk down, so now they are looser and you can still see ridges - they look like very obvious implants and don't look natural. She didn't breastfeed her baby, but I don't know if that was because she couldn't because of the implants or just because she didn't want to. Now her life has changed and she has a child, she can't afford to get the implants replaced or changed even though they look bad. With implants, if you get them young, you often have to have replacements or more surgery several times in your life, so it is a lifetime commitment - and even if you get them removed, it still leaves them saggy with scar tissue.
She has had to explain them to every man she has got intimate with since she got them, because they ARE obvious, which I think is far worse than having them discover you have naturally small breasts. Not all men like them, and while small breasts are just small breasts and beyond your control, some people will make judgements about you because you have implants - not because they are huge, my friend's aren't, but because you were hung up enough on your breasts to spend the money on them in the first place or because breast implants represent something in particular to them.
There is nothing wrong with having small breasts - they aren't automatically un-sexy, you know. One ex told me he'd had a fling with a girl who was completely flat apart from her nipples which were large, and he'd found it incredibly sexy. Another guy told me it was all about nipples for him. I've never ever been out with a guy who was hung up on the size of a woman's breasts.