I'm not even sure that's true anymore. Compete's always low-balled my traffic numbers (at least in comparison to Google Analytics) but I have a fairly small blog so I've always given Compete a pass because I can understand why it would be harder for them to measure a site with only a modest readership.

But a couple months back I got linked to by Mathew Ingram and, while Michael Arrington was covering Mr. Ingram's post on Techcrunch he also shot me a link. As you can imagine that generated a huge bump. But Compete actually had my numbers trending down for that month (cut in half in fact) and the month after as well (which was completely contrary to my Analytics readings).

So now I don't even have much faith in the site for trending data.