Why would a Steam account get suspended?
If you believe an account has been stolen or hijacked by another user, please review the Reclaiming a Hijacked Steam Account topic.
A suspended Steam account does not mean the account has been VAC banned. For more information about the VAC system, please view this article.
Check the contact e-mail address for your Steam account to see if Steam Support has contacted you regarding the reason your account was suspended - accounts may be temporarily suspended pending verification of purchase information or account ownership.
Steam Support does not automatically contact the owners of suspended accounts in most circumstances.
There is a Zero-Tolerance policy for any violations of the Steam Subscriber Agreement and Online Code of Conduct. All accounts in a user's possession for any of the following activities will be suspended:
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.
Any fraudulent credit card use, credit card chargebacks, or Paypal chargebacks (regardless of when the transaction occurred).
Never accept a gift from an unknown user. Any accounts tied to a redeemed gift from a fraudulent source may be suspended.
Do not use Steam accounts which you did not create.
This includes contacting other users outside of Steam or over the Friends network under a misleading screen name or e-mail address (i.e. "Steam Admin", "VAC Administrator", "You Won Free Game Gift") and requesting password or account information.
Accounts which have been bought, sold or traded will be suspended. This includes any other accounts in your possession at the time of the sale or trade, regardless of whether those accounts were also sold or not.