Psyringe: I don't know, IGN is probably a pretty good customer by itself. On the other hand, IGN wouldn't have the means to check whether such accounts actually got banned, and Steam is big enough to not have to bow to any of IGN's demands. It's difficult for me to estimate what Valve might or might not do, I don't do business with them myself and the second-hand reports that I see are extremely varied.

The warning relayed in the OP might be genuine, or it might be scare tactics. But even if it's just the latter, then the scare tactics have a good chance to work, because the risk is there. Valve does have the power to ban accounts whenever they deem it justified, every single one of their users has agreed to that - so your games are never "safe", your access to them always depends on Valve letting you have it.

Asbeau: Do we still get Crusader Kings for joining Prime? I really wanted that but I think I've missed it.

Asbeau: Do we still get Crusader Kings for joining Prime? I really wanted that but I think I've missed it.

prakaa: Will I be at risk of my steam account being banned?

Mohdar: I hope that users that did this intentionally will get banned.
The only thing that worries me is a possible "collateral damage" - users who got games from guys with dozens of keys hopefully won't be hurt in any way (besides deleting the game from their account of course).

Mohdar: Unfortunately no one will tell you for sure.

prakaa: To be honest, this is kind of what I've done. I signed up to IGN Prime thinking there would be a free trial, when I accidentally signed up for a year membership with no trial. Before I realised this I got King Arthur for Steam. After I realised I couldn't opt out, I did not use any more of the codes. I linked my account to an empty prepaid I had from a while back.