I just did some reading at the page you linked to (Bloom Filter) and the discussion of the math that's linked from there.

I was never that fabulous with math, but I think I get it. Seems like a good plan for a very large set. I say do it.

I had never seen the Bloom Filter, it was cool to read about. Thank you!

PS: I found the discussion of the math page to be easier to grasp. It has diagrams.

Update: I was wondering, with the Bloom thing, how do you come up with suitable functions to generate the hashes?

Update: I found this at perl.com: Using Bloom Filters