I was wondering about the same thing earlier today - got an e-mail saying that such and such added me to their hot list. I'm still not exactly sure, if I'm right, but that seems the most plausible.
I tried to create my own list and add a client, but failed - I start to think that you have to be a fully verified member who can use the client connection feature, to do this.
And basically hot list is a way for them to save our profiles under their own categories and even add some notes:
" December 2007 -- Seeking Services -- Multiple Hot Lists
It is now possible to create more than one hot list and add members to them.
Once in a hot list you are also able to record notes against them for your own information.
Create your hot lists here and add members via the usual 'Add to Hot List' link on their profile page. "
So, I'm not sure if it's of any help or use to you, but hopefully it clarifies matter a bit?
Aimee