I imagine there's that many of us who sent out emails to the various people and companies that it pissed someone off along the line... though people do get their emails hacked or sent shite loads of stuff fairly often... but it could also depend what else we've doing on the internet that could attract this sort of attention... I'd be changing the passwords to my accounts soon - we should all do it anyway on a regular basis.
Although it may be too late for some people here, it's probably a good idea to have a few email accounts for various internet related activity (one for family & mates, one for shopping, one for footy stuff, one for website registrations etc) - I'm just a bit cautious on this.
Let us know if any more people are having problems - hopefully it's just paranoia (though it could be that I registered for some 'high quality adult-themed material' from Russia that never arrived...)