As spammers are dumping links on blog comments, Google is providing blog authors/administrators with a tool to prevent certain links to be used in its page ranking algorithm: the rel="nofollow" attribute to the anchor <a> tag. Simon Willison brought us the early scoop from his investigative research.
I agree with Brian Sweeting's take, this isn't a silver bullet, despite Steve Rubel and Scoble's very understandable enthusiasm.
I wouldn't be surprised to see blogger.com update its handling of links in comments to reflect this change. Another reason why I don't run my own blog server: let other people handle the nifty upgrades 8) I'm just here to write.