Valve is taking aim at spammers with a new policy change that limits access to certain Steam features for those that have spent less than $5 on the service.
This move shouldn't affect most Steam users; if you've ever bought a game or piece of software using the service, or put money in your Steam Wallet, then you're probably in the clear.
The real target here is anyone that uses Steam accounts to exploit various features, such as Steam Greenlight voting or Trading Cards. Anyone that hasn't spent $5 on Steam -- whether for a direct software purchase, a gift card, or funds added to your Steam Wallet -- is prevented from using the following features (per Valve):
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
Steam Greenlight is Valve's community-focused voting system that allows developers to pitch their game ideas. Users then vote on these ideas, with the most popular pitches accepted by Valve for future sale via Steam. One form of spamming involves using multiple accounts to flood the voting boxes for one game or another.
Here's Valve's official explanation for the policy change. You can find more details right here.
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.