I thought the idea was you had to pay a price to play the "game", not that you were betting. Like buying an option. So the theoretical value was infinite, but the paradox comes in by the fact that you could throw a tail and have to stop before you recouped the price.
I interviewed at D.E. Shaw out of grad school. The first question is ridiculous, and I certainly saw nothing like it. The second question (about a martingale) is more viable. The questions weren't especially difficult, and all in all was a fun day. They checked for basic finance knowledge, and threw out a few brain teasers. But I had been interviewing at tech companies for years, so really all par for the course. I got a job offer from them, but turned it down for dot-com appeal. If I only knew how much D.E. Shaw paid...
This was 2000... $120k base, and I think $30k guaranteed bonus first year. They were the only financial firm I interviewed with, so I have no idea how competitive that was. I just felt compared to "guaranteed" dot-com millions, that was chump change.