basically you can get away with this if you properly take care your referer, etc. The only problem I can think of and of course this is crucial is what if your leads are asked where they come from etc, as mentioned by someone above someone did tell on him and got banned. You basically can't control this and best you can do is dont piss your leads and maybe they wont tell. and again you cant control this at all.
Probably I'll do this on my secondary account.
Coz, the most blackhat thing that you can do with cpa lead is doing adult and giving away fake promises/incentive. tho i herd they dont care if you lead your visitors to nothing after they fill out your offers.