I'm running my own mail server, using a combination of Amavis, SpamAssassin, ClamAV and AntiVir to effectively get rid of all SPAM (and you won't believe how hard they try -- it's really awful)!
Well, gmail is not the only free mail service suffering from that...
The new captcha image with random background seems to be helping to prevent automated registrations based on the number of inactive users showing up in the logs now.