Despite what Matt Cutts would have us believe (or not believe; see he can be a bit ambiguous sometimes), toolbar activity for me still seems to be a valid ranking factor.

Regarding cons of using toolbar data, the main reason would be if people were to spoof toolbar data to make a page or domain look more visited than it was. For example, at SES New York, I pointed out that Alexa provides a “Related Links” feature for web sites, and that data had been spammed to show related sites being job sites, poker sites, etc. at (Matt’s blog Alexa URL)

That resonated with me, because it showed that people were thinking about spamming Alexa’s toolbar data. Given the attention that people have given to PageRank, which is in Google’s toolbar, you can see how I’d feel about using toolbar data. I’m not going to say whether Google uses a particular signal in our ranking; I just wanted to communicate some of the potential problems in using things like toolbar data.

Just because it’s open to abuse doesn’t mean it should be stricken off the ranking factors list. Almost all the perceived ranking factors are spammable: people trade aged domains left and right, sites aren’t that hard to theme, TrustRank can be recreated and don’t get me started on PageRank. Are these factors still used today? You bet.

It could be just a matter of weightage - how much emphasis is placed on one ranking factor over another. That is the secret recipe. When too many spammers start focusing their SEO efforts on one ranking factor, they flick a switch.

Don’t we all wish it was that easy!?