Libertine Seguros said:
There used to be a gentlemen's agreement amongst the big teams that they wouldn't touch a rider coming off a ban for two years...
That was actually a UCI rule. Riders were banned for two years from racing at any sanctioned event worldwide. Then no ProTour team could sign them for two more years. This is why Hamilton ended up on Tinkof for example after his two year ban. This rule was also enforced towards Roberto Heras, though there are strong hints even UCI Continental teams were discourage from signing him, effectively blackballing him from the sport (he's not the only one though).
The rule started to get broken when the schism formed between the UCI and AFLD making the ProTour null. Though it has re-strengthened, the two-year ban from PT teams was ignored, and continues to be ignored. It may no longer be a rule for all I know.
As far as punishment, it isn't the
severity of punishment that's a deterrent nearly as much as the
certainty of it. If riders knew that there was a 98% chance of being caught when doping, they wouldn't dope. You can give instant lifetime bans, but if there's only a 10% chance of being caught - or as Bernard Kohl pointed out how he was tested the same day he doped and still didn't get caught - the length of the ban is pointless.
Also agree with Martin that there desperately needs to be some sort of whistle-blower and amnesty program for caught cyclists. It's the system of doping, including the doctors, that need to be taken down just as much as the riders.