the problem with all the add-ons you guys are talking about that use the alexa graph is that you don't really know if having it will affect Your alexa rank like the official one Will do I added it a week ago and posted a thread to get some of my members to also.
alexa is not the best way to know a site popularity, it only shows the number of times people using the toolbar has seen your site, it can be very easily manipulated by unscrupulous webmasters. but i am glad it is possible to install alexa in firefox now, maybe it will improve the quality of the information on it, at least i hope so.