I hate to throw my self into the bickering here, but:
If Ethiopians cheat because they do well then the same is true of Kenyans (distance), US/Jamaica (Sprints) and US again (Shot), just to keep the list short.
If your standard for who is cheating is who is doing well in a sport where you're goal is to do well, either lose baseless cynicism or find another past time where it doesn't matter as much (WWE perhaps).
Trollism: Despite constant calls for some supporting evidence all you have done is reference vague "public positives" and "cover-ups." Despite the fairly obvious contradiction I'd had to think you are just ranting on a message board. So do you actually have anything to back up what you say? Because right now you might as well say there is a man on the moon or the earth is the center of universe (both could be plausible, after all people believed it for a while, on their face, but are also supported by nothing, and factually wrong.)
As for people flying back to Africa after a race, I cannot speak for KB or Ethiopians, but I've heard from collegiate Kenyan runners that a lot of the Kenyan athletes will fly home almost right after a race, even if they are going to be racing again in Europe in a few days.
For those of you who think it is something nefarious that will probably add fuel to your argument, provided you think Kenyans cheat as well (see beginning of post). I just thought I'd point out that it isn't that unique.