This isn't going to be a technical question, more of an 'in world' question and that is: how does an AoE DoT determine who takes damage?

As someone who plays DRK and loves using Salted Earth, I always wonder how my party members don't end up smothering under its effect? I guess you could say it's 'caster's intent' as in whomever is consider the enemy is the one effected, but what if you have a beef with another party member and have less than positive thoughts towards them when you cast it?

I know the official reply is 'because video game', but I'd like to hear other thoughts about it.