Cool app, I think this will do well with the college scene. I just recently graduated and I know this would have come in use many times. Quick question, how are

Cool app, I think this will do well with the college scene. I just recently graduated and I know this would have come in use many times. Quick question, how are the payments handled so that the user who completes the task definitely gets paid? I could easily toss a task up there saying get me lunch and I'll pay you $50, but when they show up with my lunch I could say sorry I only have $5 to offer.