Hmm. Let me think of some of my ships.
Han Solo/Leia Organa
Charlie Weasley/Gabrielle Delacour
Well. It does seem to be that I'm all in favor of it, doesn't it? literarylemming and i share many of these ships, and we tend to refer to them as our "Lolita ships."
In real life, though, I tend to...well..not frown on them, as I really don't care, but significant age differences with one partner being VERY young (like, 18 or 19) very much raise my eyebrows and wonder about it. In fandom, obviously, with fiction i KNOW why they're together and don't need to wonder or speculate.