Artists who just seemingly randomly poof off the face of the earth without at the very very least letting their commissioners know about it, and/or offering refunds if it's going to be a long leave.
Plus-points if they also block/deactivate all their accounts.
Sure, I understand they've probably got reasons and that they might not be comfortable with sharing them, but still, a quick tiny "I'll be gone for a bit" would be very much appreciated and also slightly more professional than the whole "Now you see me, now you don't"-thing.
I'm patient and understanding, but I still like to know what's going on, especially if I've paid for something and have yet to receive it.
*Whinewhinerantrant*