You lose!..... Ummm, scratch that...

[scarsabrex]

But it says you CAN'T lose the game that turn. I thought CANT supersedes CAN.

You're correct you cannot lose the game that turn. But you can still lose life. And next turn when the upkeep rolls by if you have 0 or less life or 10 or more poison state based actions will declare your loss.

[Deathseide]

True, yet that gives you leeway, even a little bit, and stops you from dying by direct damage or attack damage, which is the majority of how people lose, it also stops the win cards like  {Coalition Victory}, etc.
This combo can easily be fit into any deck, which gives that deck a bit of advantageous edge...

[scarsabrex]

Again I reiterate

Point being it is an effective combo against most things.
If all you are doing is bashing what others work up, then go elsewhere for your kicks

Which is why I replied starting with.

Blah blah obviously every combo can be deconstructed...