I’ve seen many website or blog owners that count on Alexa rank about their web site popularity. A guy even asked $200 more on advertising only because he claimed his website is in top 50,000 in Alexa. anyone can find a good explanation about why does the Alexa is not reliable in SEOlog’s blog.
I can add that anyone can increase their Alexa rank only by downloading their toolbar and installing it on their PC.
Even it is not reliable enouhg Alexa rank is used by some of the reliable networks such as AdBrite and Text-Links-Ads. Both use Alexa’s rank to calculate the price of the advertising spots. you can however see on SEOLog’s blog that there are too many exceptions from Alexa’s stated rules, which make the searhc engine, unreliable website popularity resourse.