Who Should Pay For A Date?

Way back in the day, it was always the man that paid for a date.  Obviously we've come a long way since those days.  But how do you decide who pays for the date?

A new study shows that men are more willing to pay for a date if she's pretty.  It also works the other way around.  If the man is more attractive, then the woman expects him to pay.

Not to be shallow, but why would someone go on a date with someone they didn't think was pretty or attractive?  If I was on a date with an unattractive person, should I feel like they should pay for me if I thought I was more attractive then they were? Maybe?

So the question remains, who should pay for the date?