Question about contextual ad serving

[GlassEye]

I was looking at my hobby blog that runs AdSense -- 4 clicks since March 1st, (no applause please!) and I noticed something I hadn't seen before. The last ad on the skyscraper was for something that has nothing to do with my blog whatsoever, but is the primary keyword for my professional life.

I have another blog on the same blogger account that semi targets the primary keyphrase of the ad. I don't use the toolbar, except when I test pages for IE. I search google intensively for the primary keyword daily. I try not to click on very many adwords ads on my primary keyword, because i think it's unfair to competition.

How does google send me the AdSense ad that matches my personal preference rather than the content of the page?

[sailorjwd]

Do you have a link from one blog to the other?

[GlassEye]

I don't! I thought that would be it for sure, but I never did - they have no contextual relationship so I didn't worry about it.