In the future if you plan on taking part in ranked DotA 2 matchmaking games, you will need to attach a phone number of your account. This is according to a recent update posted on the DotA 2 website where users will have to link a unique phone number to their account in order to be able to queue for Ranked matches.
According to Valve, “Players using multiple accounts create a negative matchmaking experience at all skill brackets, so our goal is to add just enough friction to this process that the number of players doing this will be noticeably reduced. Having more players using their primary accounts will have a positive effect on both Ranked and Unranked Matchmaking.”
Basically there is a problem with regards to “smurfing”, where players create secondary accounts to play ranked DotA 2 matches on. This means that these players are free to do as they wish because it would not be their main account, which means that they can quit halfway or just screw up on purpose and it won’t have an impact on them as they probably wouldn’t care quite as much.
Valve writes, “There will be a two-week grace period from today during which players have time to register a number, but starting on May 4th, accounts without a registered number will no longer be eligible for Ranked play.”