Fuck you, Julia Stiles is cute. She's realistically attractive enough that a rather large amount of males find her incredibly underwhelming, but that's her charm; she looks like a dignified, legitimately pretty woman you might see in a college class. You may consider the phrase "realistically attractive" a synonym for "small breasted," but, again, this adds to the charm.
Kate Hudson, on the other hand, looks like she should have huge knockers. Not that Goldie Hawn did or anything, but considering the gal's face and the rest of her body, she just seems like the type to be packing D's. She played a band slut in Almost Famous, after all; one would naturally assume a cup size which, if translated into an academic grade, would result in failing a course. Unlike Stiles, Hudson's lack of boobage is an unfortunate flaw in an otherwise stellar body -- still, though, she's pretty hot regardless.
About half the pictures ever taken of Rihanna either look (A) hideous, or (B) like she's stuffed tennis balls into each half of her bra. In reality, Rihanna's lovely lady lumps don't amount to much, but they're nice enough that that doesn't quite matter. If you can't have girth, make 'em perky -- and Rihanna's love pillows are plenty perky.
Just in case you were thinking of complaining about Natalie Portman's small breasts, remember how many people were unreasonably excited to see The Darjeeling Limited simply because Natalie Portman was allegedly gonna be naked in the preceding short film, Hotel Chevalier. Big breasts or not, Natalie Portman is hot, and people want to see her naked. Again, while we may assume that breast size and attractiveness go hand in hand, Portman is actually a heck of a lot cuter without lugging around huge chest cannons; she looks a lot more charming, innocent, and attainable without them.
Ah, Keira Knightley. The woman with breasts so small that they had to Photoshop her chest for the King Arthur poster. The lady has had to deal with countless accusations of anorexia and/or bulimia since Bend it Like Beckham, so I won't beat a dead horse with small tits more than it already has been. Suffice it to say, however, that Keira Knightley should not have small breasts. She doesn't look attainable like Portman or Stiles; she looks like a classic sex goddess (look at that jawline), and it's more or less tragic that she doesn't have a body to match. Still, though. Hot.