Round robin won't work because a 25% sample is just as useful as a full feed. All they need is enough users to provide a statistically significant representatio

Round robin won't work because a 25% sample is just as useful as a full feed. All they need is enough users to provide a statistically significant representation of traffic. For you personally, if you send a query for www.example.com to one provider, and a query for images.example.net to another, you've outed yourself as browsing example.com to both.