I blogged last month about Wikipedia and SEO. There are a number of considerations when making edits, creating entries, and passing the "Notability" test -- practices to avoid so you don't run afoul of their guidelines and so on.

Well folks, the game has changed. Wikipedia just instituted nofollows on all external links. This had already been in place for a while on some of their sister sites. This effectively removes a lot of the incentive to contribute to Wikipedia. Or does it? It does if your end goal is receiving PageRank to your own sites. But not if your goals are traffic (a top ranking Wikipedia page that links to you will still drive plenty of direct clickthrough traffic your way), credibility (companies with entries give the impression of being bigger and more legitimate), and reputation management (because a favorable Wikipedia entry for your company will probably occupy a spot in the top 10 in the SERPs for searches on your company name).

So are legitimate SEOs going to give up on contributing to Wikipedia? I hope not -- at least for the ones who are adding value to Wikipedia. I think we'd all like the spammers to leave (I certainly would!), and I know that is Jimbo Wales' intention, but I doubt that's what will transpire. Nofollowing blog comments didn't drive the spammers away; I can't see it working for Wikipedia. Especially as long as Wikipedia holds the top spot for important keywords such as "marketing" in Google. (sigh!)

More discussion on this development at SEOMoz.

Matt Cutts from Google last week posted a handy tip on his new blog about how, in Firefox, to emphasize links that have the rel=nofollow attribute, which negates the vote that the web page is making by linking.

Sometimes people will say they have got a reciprocal link back to you but in actuality they have stuck a nofollow attribute on to the link so that it doesn't actually count.

You can expose such sneakiness in Firefox using Matt's handy tip. It involves creating a user defined Cascading Style Sheet (CSS) that overrides a website's own CSS.

Of course the more prevalent use of the nofollow attribute is to discount links that you have not posted on your site yourself and therefore cannot vouch for, such as in your guest book, or in your blog comments, or on your discussion forum.

When setting this up, you may want to try out a variation of Matt's solution, submitted by a commentor, that doesn't modify the original styles but instead adds a blinking exclamation point next to the nofollow'ed link.