Steam has come up with a unique way to fight against spam. Steam users need to spend at least $5.00 USD in order to have full access to all of Steam’s features. The purpose is to limit what spammers and “malicious users” can do. The reasoning behind this decision is explained by Steam as:
We’ve chosen to limit access to these features as a means of protecting our customers from those who abuse Steam for purposes such as spamming and phishing.
Malicious users often operate in the community on accounts which have not spent any money, reducing the individual risk of performing the actions they do. One of the best pieces of information we can compare between regular users and malicious users are their spending habits as typically the accounts being used have no investment in their longevity. Due to this being a common scenario we have decided to restrict certain community features until an account has met or exceeded $5.00 USD in Steam.
It’s easy for “regular users” to avoid ending up with a limited account. You can add $5.00 USD to your Steam Wallet. You can buy a game(s) that are equal to $5.00 USD or more from the Steam store. Or, you can purchase a Steam gift that is equal to $5.00 USD from the Steam store and give it to a friend who also uses Steam. To me, it seems that $5.00 USD is a low enough amount so as not to be cost prohibitive for people who are using Steam in the way it was intended.
Those who have a limited account will be prevented from accessing several features. Some of those features include: sending friend invites, opening group chat, participating in the Steam Market, and posting frequently in the Steam Discussions. Those who have a limited account will not be able to vote on Greenlight, Steam Reviews, and Workshop items.