I would LOVE it if they could stop showing Nexus One ads to people (like me) that already have them. It must be possible to read my Google account cookie and see that I bought an N1.

Possible, yes, but worth dedicating an engineer's time?

If you consider that every Nexus One ad I see is space that could be used to display other, more relevant ads to me and the ~200k N1 owners, I'd say that it is worth a few hours of an engineer's time.

Especially if you have ever visited the Nexus One landing page. Ever since, all I see are N1 ads.