Adsense displays adds that user has already clicked

[thing3b]

For the first time, perhaps ever, I clicked an adsense ad on some random site. The ad took me to the page I was looking for. It was just my luck that I lost the page.

Just wondering, I went back to the page where I saw the ad and even though the page had been refreshed (not from cache) the same ad was displayed, so I could click the ad for a second time. I got the page I was looking for back.

After a bit of testing, it took 4 refreshes and 2 clicks (honest clicks, on the same ad) before I got a different set of ads. Even after a few more refreshes, the orginal ad returns.

The page was to do with quite a popular topic, so there should have been many ads.

Any idea why Adsense would display the same ad to one user over and over again, even though they have clicked it while in the same browser session?

[jomaxx]

My first guess would be that it takes too many resources to link up the ad matching servers and the click tracking servers in real time. Remember that the whole system is distributed across hundreds, if not thousands, of servers.

Anyway just because you clicked twice doesn't necessarily mean the advertiser pays twice (or that the Adsense affiliate earns 2 commissions). Overture used to discount duplicate clicks that happened within some period of time, and I seem to recall that Google does the same. I don't know what the exact conditions are, though.