Alexa has been around for quite some time, and provides a lot of information about sites that rank in it's "Top 100,000" list, as determined by the visiting habits of the thousands of geeks who happily wear the Alexa Toolbar on their browsers. Many SEO "experts" say that Alexa data is skewed, and they may very well be correct. However, the fact remains that within the universe of Alexa "contributors" the data is very consistent and still quite valuable.
