There seems to be some serious problems with Alexa - most of the high traffic blogs including TechCrunch, Mashable, Problogger, BoingBoing and ReadWrite Web have registered a significant dip in their Alexa ranks.
TechCrunch, which enjoys an Alexa rank of ~600 during normal days, was down to ~7000 at the time of writing this post. Other top blogs have followed exactly the same pattern (see graph B.)
Graph A: Alexa data for last 6 months (the free-fall started in August)
Graph B: Close-up version of the top graph but for the last seven days
What's interesting here is that while blogs have taken a hit, the ranking of other top Alexa websites like Google, Yahoo, YouTube, MySpace, etc have remained fairly constant over the same period.
Is this a bug or can it be attributed to Alexa Sparky - the Firefox tool bar for Alexa that was released last month. What do you think?