In an article "Suspended Steam Account - Why would a Steam account get suspended?" this paragraph may be found (emphasis mine):
- Piracy or Hacking
This includes using an unauthorized ("hacked") Steam client to access Steam, attempting to register fake CD Keys or attempting to register a CD Key which has been published on the internet.
I have heard that if I register someone's retail key, he will even be able to hijack my account via support by showing a scan, claiming that it's his account.
However, I also know that some streamers officially get keys from game developers to publish them in the chat: the first one to activate the key gets it. Is it legal in terms of Steam rules, e.g. do I risk a suspension if I attempt to register such a key?