Adwords clicks vs. Analytics uniques

Why would clicks ever be more than uniques

[grigoroo]

I occasionally have days where my Adwords click stats for a given site run less than my Analytics unique visitors. I realize that the two are not synonymous, but it seems to me that if Adwords sends a click to the site, then I should see at least that many uniques. I'm dealing with approximately 500 clicks a day, and there are other marketing activities that would generate additional visitors beyond those coming from Google, not to mention regulars who come back to the site multiple times in a day. So why would I not exceed the clicks number?

[whoisgregg]

The two services use different methods to track the user, so they'll get different results. Namely, I believe you can click on an ad even with javascript disabled. But Analytics depends on javascript being enabled to register the visit.

Also, it's possible for the same visitor to search for your keywords and click an ad then search again a few hours later and click the same ad. Adwords will register two clicks but Analytics recognizes only one unique visitor.