I think I know why I get so much spam.
I'm one of several thousand subscribers to ECOLOG-L, the listserv for the Ecological Society of America. When I Google myreal name, posts that I have made to ECOLOG come up in the hits, along with my email address in full. I have been very careful to prevent the listing of my email address on the internet on other sites, but didn't realize that posting to ECOLOG would open my address to spambots in the public archives.
Gmail does do an excellent job of filtering my spam, but it occasionally lets some through and sometimes I have to dig through hundreds of messages to check for a couple of messages that aren't spam. If you're thinking about posting to ECOLOG or anything else that archives publically, consider using a different email address. I wonder if they can change the archives.