As others have pointed out, while obviously Usain ran the fastest 100m ever recorded, the fact is that the whole final was extremely fast. Tyson Gay's time was within 2 hundredths of Usain's last world record. I'd like to think they are all clean, and the evidence so far says he is... but we may not know for a while.
Could there be other technologically related reasons that could be helping the athletes? Possibilities:
- track technology - in the same way the pool in Beijing contributed to optimal swimming conditions
- shoe technology - may be giving runners an advantage over years ago
- training technology - for example, consumers have only been introduced to P90X and similar in the past decade or so. Jamaican trainers may have worked something out that others haven't in preparing their athletes, or warming up etc
- nutrition technology - better food served in ways that help the athlete in their dietary approach
- clothing technology - less air resistance, skin resistance and rubbing
- evolution - human beings are getting taller, etc.
On the subject of evolution and genes etc, would genetic manipulation be considered doping? It could certainly be argued to be cheating.