Why the big sunnies?

Aidan B over at Yahoo asks in his blog why people are still wearing those ridiculously large sunnies.

I woulda commented on his blog but Yahoo 360 wants me to sign up, so I'll stick it here.

My theory (and it's probably not very original) is this: fashions take influences from new developments in society. In the 70s it was all about colour because colour TV just came out. Now in the naughties we have a massive increase in the consumption of porn (and I've read experts are having to reevaluate their estimates on how popular fetishes are). So these porn sunnies are worn to reflect society's growing tolerance towards porn.

By wearing them, girls are unconsciously sending a signal that they are sexually comfortable. (Even though of course it's mostly teenage girls who wear them, probably the least sexually beings in our society.)