If you've spent any time managing a web site, you are undoubtedly familiar with the dreaded Alexa rankings. It's common knowledge that these numbers are fairly useless since they depend on the end user having the Alexa toolbar installed. Obviously, not everyone has this. To make matters worse, Alexa only provides a toolbar for Microsoft Internet Explorer. For some sites, this IE only restriction is not much of a problem. As you can see from the graph below, this is a huge problem for Slaptijack.

To be more accurate, this was a huge problem. On July 18th, the Alexa Sparky add-on for Firefox became available. Hopefully, those Firefox users that have been pounding the site will install the add-on and drive Slaptijack's Alexa rating through the roof!
Thanks to Doug Karr for pointing this out.
...But what would the user gain from having the Alexa bar installed. Besides a performance penalty, I guess?
@modifoo - The tool has a few tools that some might find interesting, mainly Alexa gathered information. Something a bit more useful is the "Related Links" feature. I haven't researched how it ties sites together, but I can see the value of it.
[...] Rejoice! Alexa Releases Toolbar for Firefox - This is old news of course (remember?), but still [...]
[...] Since Alexa relies on their toolbar to determine the reach of a website, I’d like to thank all the Slaptijack readers that are using the Alexa toolbar for Internet Explorer or Alexa Sparky for Firefox. [...]