September birthdays? Just exclusive enough: only one out of (approximately) 12 people qualify! It's another granfalloon, like the Red-Headed League or Hoosiers. It's so ridiculous that I love it.
And it really gets at the heart of an idea that's been rolling around in my head for a while: people are their own best fundraisers. Like all the charity bike rides where the riders try to drum up sponsor dollars from the co-workers, this encourages the Virgos and Libras out there to trump up dollars for a cause that is completely separate from them and yet completely intertwined with them.
Wouldn't it be great to help people become champions for a cause? Give them some little push: based on our survey data, you've been selected to battle illiteracy! I know it sounds crazy, but this is an idea that I really like.