Bulletproof spam hosting services (ie, internet service providers that will host your site and ignore spam complaints) are one of the techniques that spammers use to put up spam sites. Knowing that their provider will never take them down, they can put up their stuff and not have to worry about authorities coming down on them.
However, there's a bit of a cost to this; they have to pay their spammy providers a fee in order to have this privilege. To that end, some spammers have moved to abusing free tools like Windows Live Spaces and Blogspot accounts. Spammers will use bots to sign up for accounts and then upload a new spam suite. Below is an example of a Windows Live Space account:
This is a spammer trade-off. On the one hand, their costs are lowered because they don't have to pay their provider for bulletproofing hosting. On the other hand, these accounts are far from bulletproof; in fact, they are big targets because Google and Microsoft will shut down right away if they discover that the web pages are abusive. In addition, both Google and Microsoft are always working on their security algorithms so the automation of setting up these accounts is hit and miss.
In reality, these types of spammer tricks are nothing new. It's pretty much the same as the Geocities and Tripod sites outbreaks a few years ago. They are simply now using more of the free tools at their disposal.