I don't really understand how the silent treatment differs online vs real life.

If the punishment is established beforehand as it should be, and then how can it be such a detrimental thing to be ignored for a period of time while online?

Aside from that, I don't honestly know though if that would be a good punishment or not. It really depends on the couple in general, and how they choose to deal with things.
If the punishment hits home and is effective, then maybe it's not a bad thing.

I for one would probably choose that over the punishment I'm in for shortly.

That is the wonderful thing about punishments though, they are there to correct something. And punishments aren't meant to be easy, or they end up becoming a play session, which defeats the purpose.