You can drop loot on another character's portrait to transfer it to their inventory, or drop it for them to pick up.
There are no classes, so no class specific loot (though of course there will be equipment that doesn't fit with your character build). In co-op mode I think most people are going to want to try different builds, so equipment shouldn't be much of a problem. I suppose one person could gab most of the potions, etc, but if the combat is balanced for 2 characters they are going to start running into trouble if their greed ends up handicapping the other player (assuming their behaviour doesn't outright discourage others from playing with them).
Also, there is friendly fire in the game. You can always 'accidentally' hit someone with a fireball, and then say "oops, sorry, I was just distracted thinking about that 4th time you grabbed loot in a row and didn't give me anything."
