STEALING 1:
If you are killed by the mob (or by environment) you drop your stuff on the ground. You can resurrect and reclaim it if you are quick enough. However, if someone else is quicker he can also loot it from the ground, and in that case THAT is stealing.
STEALING 2:
If you killed a mob you get loot permissions on it and you can loot it. Someone else can loot the mob too if he is quicker than you to its corpse, but in that case THAT is stealing.
Those were 2 cases of stealing that I think devs were talking about.
OTHER:
There was no mention of pick pocketing of any kind, but who knows. Maybe we will see that in game too, there is still long way to go.