In general, people should take Alexa rankings with much bigger grains of salt than they tend to, but I'm glad to see they've now combined blogger.com & blogspot.com traffic, so as to make easier comparisons. (And because I like to see the chart go up real steep like that—I'm still slightly biased.)
(The biggest problem I've found with Alexa is that Alexa is highly biased toward US-based users. More than half of Blogger's traffic, for example, is from overseas.)
Update: Rabble tells me Alexa is also biased a lot toward Koreans. Which, from what I've heard, may explain certain other site's surprisingly high ranking. (Not that said other sides aren't cool.)