I just received my very first spam on the account I dedicated to Gravatar. No thanks to the blogger who displayed my e-mail address unprotected on his site.
That’s why I signed firstname.lastname@example.org every time a blog demanded an e-mail address, and I’m not sure that Gravatar will ever catch on if they insist on checking the validity of addresses.
P.S. And Opera is too dumb to exempt outgoing messages from the manual anti-spam filter I’ve just had to set up.