Unless they are a competeing company, what ever happened to professional courtesy?
If you are worried about litigation, remove your title block &/or have them sign & return a legal document releasing you from all liabilities. That is what we do.
Sometimes companies / people get so high & mighty about CAD dwgs. I had one guy tell me "I've go many hours of work into these, I'm not going to give it away'. He had already been paid once to draw them for the customer. All we need was the floor plan, none of the piping, etc...
I guess I can understand selling your CAD files if it is a reproduceable item, like a house design or such, but for a particular building, I think it is childish to hold &/or charge for them.
craigr