If you don't think doping is going on at the highest levels of every sport, you're naive. That doesn't mean you have to scrutinize specific athletes, trying to discern who is/isn't using, it just means that a shocking percentage are doping. Radcliffe is suspicious because she is at the top of the sport. I don't care how squeaky clean you appear, if you are at the top, you are immediately more suspect than most.
How many times have we seen athletes be outspoken against doping, deny doping, only to be caught? How many times have athletes been caught without a positive test? So many athletes are protected by governing bodies and/or sponsors which makes them invincible. Lance Armstrong and Carl Lewis are perfect examples. Both were protected by governing bodies and Nike. I guarantee there are Americans in track and field right now who are protected and dope without a second thought because it can all be swept under the rug with a bit of money. That is why folks like Armstrong can be outspoken, because they know a positive test would probably never occur, and if it did, it would never see the light of day.
The Tyler Hamilton book is ridiculous if you haven't read it. This guy was doing multiple drugs and transfusions in the lead up to competition, on competition days, and right after competitions. It took him awhile to finally test positive. If he avoided a positive as long as he did, while doping as extensively as he did, you can bet others are doing the same to this day.