Now I'm not one to rake mud, however...
Nigel Adkins was sacked by Southampton for having his hand in the till, and that's also why Malky Mackay was sacked by Cardiff, so they're two for starters.
And one of them has got to be Redknapp who would sign trusted players for all the different clubs he moved too - didn't he sign Nico Kranjcar three times?
Having said all of that, almost every industry that I've worked in has involved kickbacks being given and taken. Perhaps not to the same extent, or size, as football, but it's all relative. Not that it makes it okay, either.