The Right Way
eBay should be congratulated: this is the right way to handle targetting advertising, completely unlike Phorm.
1) If I am going to receive advertising on eBay, it may as well be targetted instead of random
2) If I do not want targetted advertising for any reason I can opt out
3) Most important of all, this is not snooping on my private communications like Phorm, it is limited to making use of what I view and buy on eBay
The only things missing which I would like to see would be an assurance that eBay do not send personally identifiable data to the third party ad selection engine they use, and a notification of who that is.