Leaving aside the question of whether the Alexa web traffic monitoring system (owned by Amazon) is Spyware or not, I was asked this week how accurate its figures are.

Testing one of our sites which we know receives 19,000 visits per week, Alexa came back that we were actually getting an average of 1.6 visits! Clearly this is a fair bit out.

This article seems to confirm our result, and explains how easily the system can be abused...
http://www.mediacollege.com/internet/utilities/alexa/