This is what happens when you assume. A big reason why I wanted to do the Top 25 ranking for Marketing blogs here (and Advertising blogs at BMA), is because I assumed that most bloggers were familiar with Alexa, and their traffic rankings according to Alexa.
Seems that's not the case.
So for anyone that I have tee-totally confused with this Top 25 rankings, let me back up and give a poor-man's primer on how Alexa determines your traffic-ranking.
First, Alexa uses your 'actual traffic', as well as your page views in some secret formula to determine your traffic ranking. This is different, and IMO more accurate, than link aggregators such as Technorati, because it does attempt to measure actual traffic. All Technorati does is count links, and anyone can pass around links.
Now for the 'bad' news. Alexa only tracks the traffic of your blog's visitors that have the 'Alexa toolbar' installed, and this toolbar only works currently with Internet Explorer. So if someone visits your blog and doesn't have the toolbar, then they aren't counted. Likewise, if you add the toolbar, every visit you make to every blog/website is now counted.
Disclaimer: I do have the Alexa Toolbar installed on IE, but I use Firefox for my browsing. I do use the toolbar when I want to see what a blog's Alexa rankings are, because it instantly gives you that ranking when you visit the site. The Firefox extension I have that gives the Alexa ranking sometimes lags.
So in the end, Alexa isn't perfect, but I do think it's more reliable than Technorati. If there's something else you don't understand about Alexa, leave a comment here.