Littlebits said:
I'm sure other websites will do the same because they need to targeted ads in order to stay in business.
However you can still opt out of Yahoo advertising- http://info.yahoo.com/privacy/us/yahoo/opt_out/targeting/details.html which will stop most tracking.
The opt out is recorded to your IP address and once you opt out it will apply to all browsers running from your IP address.
It's actually cookie based. Opting out will place a persistent cookie on your machine. In order to opt out multiple machines, you need a Yahoo account. (or I guess set the cookie on each machine...)
Not the ideal solution, if you ask me. :s