It looks to me as if the new generation of T20 batters are going the same way as baseball sluggers - in other words getting into the whole body-building culture, including performance enhancing drugs - many of which are undetectable.
When I say 'looks to me' I mean that there is a fairly characteristic body shape and coarsened facial appearance (heavy brows, prominent lower jaw) which many of these drug users develop - and I think I see some of these changes in some of the big hitting T20 batters.
If this is the case it will, no doubt, be quite well known to insiders - as was always the case in baseball where heavy drug use was endemic among the most successful batters for many years before there was any attempt to stop it - and even after testing drug usage has remained very widespread.
Partly the big money to be made; but also the one-dimensional and simple nature of T20 batting makes it the kind of sport where drugs can make a significant difference.
Hitting sixes is at a premium, and this requires strength and bat speed - both of which are amenable to drug improvement.
And the organizers want lots of sixes, so there is a conflict of interest with respect to detecting drug use; as also happened in baseball with their equivalent of home runs.
The increased frequency of baseball home runs was very popular with fans; for example in the Sosa v McGuire home run record breaking chase of 1998, now presumed to have been drug-fuelled, and of course the remarkable drug-revived career of Barry Bonds.
Test batting and first class cricket, by contrast, is so multidimensional and strategic that drugs would probably make it worse, by 'messing with the mind' as they do - and many of the best T20 batters are mediocre at the longer game, which fits the pattern of drug use.
Up until now, the main (detected) use of performance enhancing drugs has been the relatively-benign situation of anabolic steroids apparently being used by bowlers to speed-up their recovery from injury (this would fit the most most famous example of Shane Warne).
If it is suspected that T20 batting may be drug-fuelled, then it is unlikely to be prevented by drug testing, since the sports pharmacologists are always a step or two ahead of the testing regimes (even when testing is applied non-corruptly).
What is needed to detect drug use is the kind of police detective work which led to the exposure of Lance Armstrong - discovery of laboratories, chains of supply, evidence of corrupt coaches and patterns of usage.
Detection would be a complex and expensive business, in other words.
Given the fact that both top players and T20 organizers benefit from the six-hitting abilities which come from the culture of performance enhancing drug usage, I don't suppose it will happen.
Note added 10 Oct 2013 - This article by John Hotten independently came to similar conclusions about performance enhancing drug use in T20 as this one, but a few months earlier - http://www.espncricinfo.com/blogs/content/story/622827.html