Ads for my site on my site

Why would anyone do that?

[mzanzig]

I came across a very large video sharing site that recently got acquired by the market leader in Internet search, and I noticed that they are displaying Adsense ads. (To stay within TOS of WW, I can not go into the specifics here. :-)

Now, to my utter amazement, the first ad in the leaderboard on the top of the page was for their own site, something about seeing Top 10 videos. What's the point of this? Shouldn't Adsense automatically detect that an ad for your site will be displayed on your site and block it? I mean, whenever someone clicks this, it costs the site real money, even if it goes from left pocket to right pocket.

[trannack]

They need to block their own domain name in adsense - obviously otherwise people will go round and round in circles. I am aware of this situation, it happened on one of my sites, I had (wrongly) assumed that google didn't show your own site adverts on your site - not so. Bit of a glitch in adsense I think.