While some put a lot of stock into websites such as these, I would encourage you to not do so. As they may offer one point of reference to figure out the worth of a website you own, are selling, or would like to buy, they should just be one of many other statistical references to gather data from. If nothing else, they offer a form of entertainment, and you can grab a nifty website badge from some of them to impress your friends and co-workers.
What a great resource! These folks have done simple training videos on many of the most popular and functional solutions around for Twitter, Wordpress, etc. This is a GREAT starting point to build a base of knowledge.