"In mid April, Digg approached the worldwide reach of Slashdot, formerly regarded as the most widely read tech site on the net. People had been speculating about the event for some time. Then, on April 19th, "it finally happened," writes ejoyner. "Digg overtakes Slashdot" is posted and the story instantly hits the Digg front page.
Hundreds of thousands of Digg readers follow a link to Alexa en-mass to see internet history being made. Some percentage of them install the Alexa toolbar that very day, and the head-count that this percentage represents is huge enough to significantly skew the Alexa demographic from that point forward..."
-OR-
"Something you've got happening is a negative number of slashdot readers - something that is impossible. You're assuming a continuous amount of users kept the Alexa or A9 toolbar installed. I'd actually think that slowly the numbers would reduce as more and more people ran spyware checkers that delete Alexa components, or otherwise removed the Alexa software once they realised what was going on.
This seems to happen more with slashdot readers than digg readers. Does this mean that slashdot readers are smarter than digg ones? Arguably, digg has a much younger demographic who are more likely to run Windows, and are more likely to fall in the "wannabe geek" category.
This is why Alexa is useless and anyone basing their web traffic stats (particularly geek-oriented ones) are hitting the lowest common denominator - a group who don't know what spyware is or how to get rid of it."
(Digging Alexa - how the geek demographic doubled overnight | BlogCadre)
