I use to play on Full Tilt with guys from work all the time.

Quite often I would be at a table with someone I know and chatting on the side.

We wanted to beat each other though for bragging rights so never colluded. Thinking about what could be done though if sharing card information is really bad. There are so many spots that knowing for certain 2 cards have been removed from the deck would be an absolutely massive advantage.

I can't even imagine the schemes real cheats have come up with.