I believe wordpress is sending something which alerts the spammer right when you install, and my guess is that the bot he uses probably reeds the pingomatic rss feed which comes by default in the wp install. You can find it in the ping section, Options>Writing. http://rpc.pingomatic.com/
Do you know what I mean? Yes! you start getting spam right after install, don't you find that suspicious?
I recommend that in version 1.3 they erase this domain from the opitions section.
So my advice. Just after you install, while you are configuring, erase Pingomatic BEFORE YOU DO YOUR FIRST POST!
Good luck and happy blogging!