Valve is introducing Limited User Accounts in order to battle spamming and phishing being done on Steam through suspicious account holders.
Your account is categorized as a Limited User Account if you have spent less than $5 on Steam since its creation. As such, Valve will be taking away access from such users of certain key features found on Steam.
These restricted features are the following:
- Sending friend invites
- Opening group chat
- Voting on Greenlight, Steam Reviews and Workshop items
- Participating in the Steam Market
- Posting frequently in the Steam Discussions
- Gaining Steam Profile Levels (Locked to level 0) and Trading Cards
- Submitting content on the Steam Workshop
- Posting in an item’s Steam Workshop Discussions
- Accessing the Steam Web API
- Using browser and mobile chat
To upgrade your account from its limitations, you’ll require to add $5 or more to your Steam wallet, directly purchase a game that is $5 or more, purchase a Steam gift that is $5 or more, or just add a Steam Wallet card which matches the same figures.
It’s important to note that activating a retail game, or receving a gift will not remove limited user restrictions.
Source Steam Support