I don't personally know of anybody doping in master's track, but apparently it is rampant.
Like d, I don't compete in masters stuff--just open meets. My mid/high 11.x still lets me finish within sight of the winners, so I'm still OK. As soon as it gets embarrassing, either in a meet or in practice, I'm outta' there.
I would love to know the feeling of doping, with my torn rotator cuff (getting better), and my currently torn butt/ham (also getting better). I've never been invincible, I have had these types of "nicknack injuries", as Gatlin termed them, ever since I can remember.
I can totally see that at some point, masters are presented with a decision: either cut back a lot or quit to maintain health better, or dope to continue training and competing.
My choice will be an easy one, since I have a life, and am not trying to recapture high school glory, as are many. I think when I quit to do some different sport, I will try my hand at informal coaching of kids, to stay around the track.
Hopefully I will have another decent couple of years, where the injuries are at least manageable.