I think Alexa is only valuable for getting an idea of where you stand (assuming you operate honestly) vs other sites which you trust are also operating honestly.

I saw on another webmaster board recently outlandish claims of their Alexa rating. I checked their Alexa rating and it was true that they were ranked where they said they were, but it didn't add up. They would need 1,000 gay webmasters online on their site 24 hours a day all day using the Alexa toolbar in order to substantiate their claim.

That begs the question of how they do it. I'm not sure... Could it be, perhaps, something like: http://www.fakerank.com? Or how much would it cost to have an army of folks in the Phillipines install the toolbar and click around on your site all day? Less than you might think.

Our alexa rating is real and I know what are pageviews are, so I have an idea of how big a site needs to be to be in the rankings in the above 15,000 level.

So Alexa is valuable to me when I want to compare myself against another site that I know wouldn't stoop to manipulating results. But, I think there are some around who know how to play us... or at least try