I never address the issue of donation until the session is over. If someone arranges a meeting with me with specific purpose of ripping me off, they are going to do it and escalating conflict won't end well.
That said, I operate under two premises:
1) You get to fool me only once
2) As I mentioned in another post - I have no living enemies.
On serious note, people should "screen" each other not just for safety but for compatibility as well. Just because we live in universe of no strings attached encounters, we still are better off by seeing people we click with both mentally and physically. Research and you shall find what you seek
Lina