OpenRA

http://www.youtube.com/watch?v=GkLBFDzqo9c
In the game above, Microbit has abused this tactic successfully 5 out 8 attempts, using Light Tanks as the blockers.

I have them marked by time.
3:35 - Ore Refinery
3:50 - Fail
4:55 - Fail
7:15 - Ore Refinery
7:30 - Ore Refinery and then Barracks
8:30 ...