In an effort to stop some of the more negative aspects of online play in DotA 2, Valve has announced a number of sweeping changes to ranked play, including forcing players to provide a unique phone number in order to compete. That number will be registered to your account, so it should become much harder for people to create one time, throwaway accounts to troll others or smurf their way through the ranks.
Of course this wouldn't necessarily stop people doing it entirely, but it should make it a much more time-consuming practice, which should help weed out at least a few of those who do so otherwise.
This change is now in place, with players having until May 4 to set up their new account phone number. If they don't, they'll be locked out of ranked play until they do.
To try and match the lack of cohesive support often found in games made up of Solo players, Valve is also implementing a new solo-queue which will be made up entirely of those who don't have teammates they know.
Solo players with really high ranks will also be matched with teammates closer to their range, even if they are playing in team games - to make sure that the skill level between players is comparable.
One final measure to try and rid the game of disruptive players, is added rank bans for 'low priority' players and intentional feeders will be detected more easily according to PCGN as well.