Don’t get me wrong, Alexa can be a valuable service, but their data doesn’t match up with our own carefully analyzed logs, Mediametrics, and other services like compete.com.

Rather than simply acknowledging the possibility of sampling errors, a blog post from Alexa titled Alexa Data vs. Your Raw Logs shifts all blame to site owners, saying that they don’t know how to analyze their own logs:

We occasionally hear from users asking why Alexa’s traffic data for a site doesn’t match the data from their site’s logs…

Few individuals are sophisticated enough to read their logs and understand what they mean… You can’t reliably detect fraud or crawlers or many of the other factors mentioned above that have a drastic impact on your reported visitor number.

Anyone, anywhere, can download the Alexa toolbar and contribute to the stats.  There’s not a single mention of possibly inaccuracies caused by the fact that Alexa’s “panel” is self-selected, nor any details behind Alexa’s seemingly magical claim to be able to distinguish fradulent users of the toolbar from legitimate ones.

Rather than increasing trust in a service, self-serving propaganda like this decreases my level of trust. 

 (For the record, some of the other sites like compete seem to have much more representative stats than Alexa these days.)