Google is now honoring the rel=”nofollow” attribute in link tags. Basically what this means is that links in comments, and links to your competitors, or links to things you hate can be eliminated from consideration in computing the page rank of the destination page.
MSN search and Yahoo are also adding this:
On the one hand, I think this is a great idea and a long time coming – I’ve often complained that links aren’t all alike and should be treated differently.
But, on the other… I run a small blog, and I get a lot of my page karma from comments I put in other blogs. I don’t see that as necessarily wrong – my comments are always on topic, and if the owner of the blog doesn’t agree, they can always delete the comment or the link. Google isn’t tracking clickthroughs (yet), so they have no way to know if a given link in this context is actually popular or not. Automatically including this tag in the comments section may decrease the level of comment spam, but it’s also going to hurt a lot of small bloggers as well, I think. And if you’re reading the links individually to make the distinction, well… why not just delete the spam ones? This is obviously meant to be an automated measure, and it’s going to catch a lot of legit links too.
It’s just pushing the unknown down one layer, and substituting one set of unknowns (owner links vs. comment links) for another (legit comment links vs. spam links).