Chained Payments - Can people not pay you?

Hi all,

So I havent setup my Marketpress Mall yet but will be very soon. I was wondering how chained payments work and found out but my questions are now that I know:

Whats to stop the initial receiver just not paying you the commision?
Do you have to initiate a Payrequest for every sale or can you wait until its totalled up a bit or what?

Cheers dudes