If that's the case, you're going to want to focus more on statistics and trends and less on /whether/ or /why/ a tracker is down. You're also going to have to pay careful consideration to how your own operation can unbalance currently stable situations.If your site promotes the most stable trackers--which will be a direct result--then those trackers will get so much new traffic as to overload them. There'll need to be some kind of real-time, per-user round-robin distribution of attention, and the standards need to be low enough that the pool of trackers considered 'reliable' is not too small. It can't just be a tool that points to top dogs.