What happened in this video is that Terran did an all in very early game with 10 scvs stacked (looking like 1 scv), plus some marines. The stacked scvs went up the ramp first, and the Protoss did not FF because at the time he only has 1 force field and it was saved up for the marines. Then, the stacked scv opened up and surrounded the protoss units while the marines went up the ramp and ended the game.
I have no idea how this stacking is done, but I highly doubt this is designed as there is no way to differentiate the stacked scvs from a normal scv.
This post is to warn you about this new "strategy", and discuss ways to stop this timing.
Edit: OK GUYS, the problem here isn't that "you can stack workers", the problem is that you can stack 10 SCVS to make them look like 1 SCV. Now that's deceiving. When you have only 1 FF and you don't notice the "brighter scv", its easy to let them go through. This THREAD is a WARNING thread.
Edit 2: this thread talks about TvP specifically. Please do not use "Oh any race can do it therefore it's balanced". Each MU is different and in PvT Protosses rely on early force fields to survive. I wouldn't stack 10 probes into your mass marines in any circumstances.
:< must know, how its done.. And this should be in the strategy section by the way.
(prolly just stack on gas) answer is just have a probe scouting, if you see 1 scv and a bunch of marines... Expect there to be more than 1 scv in that stack.. forcefield ramp chrono boost out 2 more sentries.
What you do is spam click SCV's on your minerals so they get clumped up, then on another patch in your own base so they move there, move your camera to opponents base, and click on one of their minerals (so the SCV goes to mine there).
At least I think that should work.
You can see it by box selecting the scv I'd assume.