The incentives being bigger is of course also more reason to cheat.
I'm happy with every new catch, and hope that this means detection and testing are catching up to the methods of evasion-- which I don't really know the details of, since this is not the type of science that gets published in the typical scientific journal.
I'm not sure why both rojo and flying fin are annoyed that people are speculating without having all the facts-- face it, the public will never have all the facts. So we talk about our sport with what we have, even though it's not much. Should we just say nothing? People get to have their opinions, and any time there are breakout performances, it would be naive to not consider PEDs.
I do think the recent number of Kenyan busts is interesting, since it seems to contradict the old saw that all Kenyan runners were pure at heart, and never would ingest even an aspirin. I frankly think that's ludicrous- people are people, and you dangle enough of a reward out, they'll do anything to get it-- whether it's training ridiculously hard, or taking PEDs, or both. Plus, as the sad story of Wanjiru shows, Kenyans can ingest alcohol as well as any other people, which seems to be in conflict with the whole "they would never take anything that would hurt them" mindset.
Finally, I think it's interesting that in cycling, not only are times not getting faster, they're actually slowing. They have the benefit of being able to study power output, and the science of sport blog had interesting analysis of how power output on the beyond-category climbs was down from 6.2-6.4 watts/kg to 5.8-6.9. That's a 7% drop. If we take slower times in cycling as signs of a cleaner sport, it's a bit naive to say that all the fast marathon times (and recent 5Ks) are just the result of bigger incentives. It's one possibility. But there are others, and it's pretty ridiculous to imply that fans of the sport can't speculate about the others.