Payperpost announce segmentation.
The ethical question still surrounds payperpost but this feature is a huge improvement for advertisers. I would reconsider using them again even, if I had the budget to do so. What this means is now rather than just throwing your ad out their to anybody you can set credentials that the sites picking up your ad must meet.
This include PR, Alexa ranking and category of site. Everything that the service should have had included from the start really.