Seeing how hookers might show up on an expense account reminded me of a question I had about sixdegrees.com a while ago. Amongst the relationships you can say people have to you, there's no obvious choice for someone who isn't a "Significant Other" but is a bit more than a "Friend." Since "Umfriend" (as in "This is my...um... friend...") or anything of that sort didn't seem forthcoming, I looked through the list of possibilities, and settled on:
"Service Provider"
When you think about it, it seems a bit suspicious in the list there. Especially since most ISPs aren't individuals, and there's not a different term for the reciprocal relationship...