Does google care about the traffic, like alexa.com do ?! Some people says, that google can use the google toolbar for submiting your website to a category. Like if lot's of people who visits "AAA related" sites, will also visit your website, and your website is also "AAA related" then you will rank very high for AAA keywords... what do you think about this!? Anather Phantasy !? or is true?!
Personally I don't see how they could use this method to affect rankings, as all you'd have to do it hire sweatshops (or even use scripts) to visit your site on a regular basis and away you go. If it's using the google toolbar then you could simply hack it to send off your website(s) URLs every so often, thus artificially inflating rankings. Then, what about those ppl who don't have a google toolbar? It would skew the results unfairly if your userbase used the Gbar and your rival's didn't...
Without some type of way of tracking this "traffic", I hardly see how they could base rankings on it.