Valve are trying to clean up the Dota 2 community and make matchmaking better, with some big changes being done.
First up, let's talk a little about the recent major ban waves. Valve said they have removed players from Dota 2 with "exceptionally low behavior scores" and they will continue to do so regularly, which is good and very much needed to keep the online community healthy. They have also done a second ban wave for anyone who has been "detected of violating the Steam Service Agreement that prevents the purchase or sale of Steam accounts"—ouch. A third wave happened, to remove players who've been using "exploits to gain an advantage over other players" and they will be adjusting how they detect such things over the coming weeks.
Not only that, bans will also now block the phone number associated with the account permanently, so people will have to setup a new phone making it more difficult for nuisance players to come right back. Linking directly with that, Valve said they closed a hole that allowed "a large number of users to play ranked without a unique phone number attached" to help against smurf accounts. On top of all that again, to gain access to Ranked play you need to have 100 hours logged in the game.
Amusingly the bans are listed as being until January, 2038. They are permanent though, it's likely just the way Valve are storing the dates has the "Year 2038 problem". They probably need to adjust their database to support a different time storage method.
As for matchmaking, they continue to tweak the new Role systems in place. Part of that is ensuring that the games are actually balanced. They're going to be putting a larger emphasis on making sure that the roles are more symmetric based on player ranking rather than just spreading the rank across each time and making it match up.
There's a new reporting option included too, as some players were not playing properly as the Role they queued up for so Valve said they're going to be a little more "aggressive in punishing players who abuse the system".
There's more to it, see the full blog post here.