I got matched up with a guy who decided to do that once. Admittedly if the guy he chose to attack wasn't a level 12 and didn't know the game, we probably would have won, but the bad thing is... is that he wanted to attack all on his own when he did it, and told myself and my other team mate about it. So He severely lost that battle resulting in a counter attack that wiped us out.
So yeah, it does work, you just have to know what the hell you're doing. It's just like any other tactic... just keep your lines of communcation open.
Personally I think it sucks, because while your buildings are attacking, you aren't building buildings. Therefore if you lose, your team mates are then put in a 2v3 situation while you scramble to build up... and it isn't likely that you are going to help for a while because you went and destroyed every building that you've built.