I guess Gmail is not a web-based e-mail service?
It is sad that one spammer could suddenly disable tens of thousands of honest people's accounts.
Too bad, because Gmail actually blocks spam to Gmail accounts VERY VERY well.
Instead of banning 100% of Gmail, Yahoo! Mail and Hotmail users everytime a spammer signs up for an account, can't you just forward the offending spam e-mail to Google and have them disable the spammer's account? I think that would be much more effective, especially since Google has an interest in terminating spammers and has a policy against spam, just like Yahho! Mail and Hotmail.
I mean, this isn't like you are dealing with a shady company.
I hope this gets resolved soon. I know Google does not want their system used for spam.