Yahoo, Google, MSN, and others all join hands in an attempt to reduce weblog comment spam.
The idea is to have search engines ignore links in comments on weblog posts when computing PageRank, somewhat reducing the incentive to engage in comment spam.
I say somewhat because there's value to spammers in having a link or even just a mention of a product name in a public forum. The proposed solution will prevent spammers from improving their rank in search engine results using weblog comments, but that's only one of several reasons spammers spam.
The problem is similar to e-mail spam where, at least for some, the value from the tiny number of people who respond positively to the spamvertising exceeds the very low cost of sending out the spam. Raising the cost of spamming also has to be part of the solution.
See also my earlier post, "Killing comment spam".