You search for a game on Battle.net, the countdown starts and at the same moment your telephone also starts ringing. Suppose you want to take that call.
Is it considered a loss if you logout or close the game before the actual game begins?
According to the patch notes released today:
A player who logs out of the game during a match countdown now receives a point loss. The other player now receives a message that the opposing player has canceled the queue and neither receives a point bonus nor penalty.
So yes, you will take the loss by closing out/quitting the game.
Source: http://us.battle.net/sc2/en/forum/topic/5271506462?page=1
Yeah, it ends up in a loss. Here's Destiny raging about it.
Yes
so how can any other answer be correct?
This answer is now (with Patch 1.5) outdated.
If you manage to logout in time you will get a tie, as shown in the picture below. I guess if your computer freezes or you try to Alt F4 you might get a loss. The following reasons might apply: