What's the difference between a socialite and a philanthropist?

Apparently, a socialite actually gives the gifts that are promised:

The Metropolitan Opera has received the largest individual gift in its history, a $25 million donation from the socialite Mercedes Bass and her husband, Sid R. Bass, that comes at a time of increasing financial troubles for the house.

Contrast this with:

In effect, the gift to the Met replaces the unfulfilled pledges of Alberto W. Vilar, an investor and arts philanthropist. The Met added Mr. Vilar's name to its Grand Tier in recognition of a $20 million pledge several years ago, then removed it when he failed to meet the pledge. Mr. Vilar has since fallen from grace with his indictment on fraud charges in June.

Wouldn't you love to see the social stylebook that describe the two professions?

Oh well, when one Texas benefactor exits...

UPDATE: Angus, despite what he says, didn't "lift[] this from [me]" unless we're in a universe where 10:29 a.m. Eastern is somehow after 10:52 a.m. Central. Are we and I didn't get the memo for the day? (If so, I need to know before my lessons schedule gets all screwy on Monday...)