The is not a WordPress issue, but I get frustrated when I see people want to give credibility to the Alexa website rankings.
Alexa is a service owned by Amazon.com that ranks websites based on the amount of traffic they get. The problem is that they do not know how much traffic a website actually gets. They estimate the traffic based on visits to a website with the Alexa tool bar installed in their browsers, which is only an extremely small percent of internet users.
The problem with the Alexa rankings are:
1. It is extrapolated from that very small sample.
2. That small sample is biased, as the tool bar is typically used by those that are more tech savvy so will be biased towards the sorts of websites that those types of people typically visit.
3. It is easy to manipulate. All you have to do is install the Alexa toolbar and visit your own (or whatever site) several times a day and you will improve the Alexa ranking.
The Alexa ranking really serves no purpose other then entertainment. It is not used by any search engine as a factor in their ranking algorithms.