Valve actually offers quite a bit of leeway in using their service, so getting banned is not something that's particularly easy to do so long as you follow the rules. There are simply restrictions added to the account but the content you paid for is content you still have access to. This means that gamers who have been banned either for fraudulent or nefarious purposes with the intent to use their Steam account for other activities other than gaming like an upstanding member of the interactive entertainment community, can still access the games they paid for.
