The North America and Latin America regions will be linked, while Europe connects with Russia, and Korea with Taiwan. Players in linked regions will be able to player with their new buddies, in custom games and in matchmaking, and be able to add them as friends. It'll help smooth things over for players in less-active regions. This'll happen when Season 3 of the StarCraft 2 ladder kicks off, which is currently scheduled for the week of July 18.
"Having a larger pool of players means the automated matchmaker for ladder games will be faster and more effective at finding opponents at or near your skill level. Similarly, more players means faster queue times for custom games, which benefits both players and map creators," Blizzard explains. "From a social perspective, players will be able to create character and Real ID friendships with people from the newly linked region, which they couldn't have before."
Blizzard insists that "There should be no impact on game performance," explaining, "All players in the linked regions will be connecting and playing through the same data centers that they were using prior to region linking, which is the main reason why linking these regions together is fairly straightforward."
Unfortunately the divide between regions is not being outright demolished. Australia and New Zealand are left in the lurch in the South East Asian region, and European players still won't be able to play with their American Internet chums. It's certainly still a welcome move, mind.
Thanks to Shacker 'Mandoca' for the tip.