Question: is there a way to do it without address-book crawl? E.g. a field where you could input a list of e-mail addresses you want to search for?

More cumbersome, but wouldn't produce the instinctive AAAAAAH MY E-MAIL PASSWORD WHY ARE YOU ASKING FOR THAT skincrawl.

And it would also mean it would work for people who aren't using Gmail/Yahoo Mail/Hotmail (or who are using another e-mail program as well as a web-based one).