I did it in 2010 with Sidney Rice (PUP after hip surgery) and Vincent Jackson (holdout). The problem was, neither came back when expected and I lost a lot of games waiting for them. I made it to the playoffs though and they each posted solid games for me. I was a Knowshon Moreno injury away from a championship.
Peyton Manning last year's another example
Injuries always have the potential for slow recovery, aggravation, etc. and there's always the possibility your discounted player may take longer to come around/come back for short while before going down again/or shut it down for the season even (i.e. Peyton 2011).
Guys facing suspensions w/ elite talent, or problems w/ the law, can be good discounts. Sure they may be boneheads, but at least you know they have elite talent when they're on the field (i.e. Dez Bryant). Unless their issues are uber criminal, you're only looking at a slap on the wrist for a few games tops.