Internet marketers always want to know how well that their web site is doing compared to their competitor's websites. The problem is that it's impossible to actually get the backend information of their competitors to learn how many visitors that a website is getting. You can view how good that they're ranking in the search engines, but you do not know how many visitors that they're getting. One place that many site owners use is the traffic rankings available from Alexa. They use information gathered from users that have their toolbar installed in the browser and record information on the websites that they visit. Based on this information they give a ranking of all the web sites based on the traffic. A major issue with the rankings is that they are biased towards the types of websites that those who are more tech savvy tend to visit, as it is only these kinds of people who tend to install the toolbar. Individuals who are less tech savvy, usually do not install the toolbar and in all probability are likely to visit different types of web sites.
The issue with the Alexa Ranking is that it is really easy to fake that you really do not know if what you see is true or if it has been managed by your competitor to look greater than it really is. All you have to do to artificially inflate the Alexa ranking is install the toolbar on your computer and just go to your web site repeatedly each day and then watch as the Alexa number improves. Better still, get a few friends to do it as well. There are even paid providers that can do this for you to artificially increase the rating. This is the reason the Alexa ranking number is possibly not really worth spending much time on as it is really easy to control.
The last word on the Alexa ranking is that it is just that, a rating of websites based on site visitors that is easily controlled. No search engine makes use of the Alexa ranking to rank websites, so there is no advantage to having a good Alexa rating.