Fully random maps in SC2?

Solution 1:

I may be mistaken, but I think the change in fog-of-war is one of the changes between Starcraft 2 and Broodwars. The idea is that the map is no longer unknown (as that benefits users who spent the time memorizing maps from their starting locations).

Solution 2:

While I can't help with the fog of war, if you want the game to pick a random map for you, go to Multiplayer and then create a game. Add as many AIs as you want, change settings, etc. and then start the game. Your map will be chosen for you.

As an added bonus, playing multiplayer will help you work towards achievements too (why they don't work in single player as well, I do not know).