I was the options market maker for Hedgestreet, the predecessor to Nadex.
The winners on the exchange used to game the system by entering standing orders to buy low and sell high at the nearest strike five minutes before expiry. To combat we'd widen the spreads close to expiry, there was no...
Exactly, I watched many people trade themselves into the poorhouse while options market making. Main thing if you're going to trade options is always leave yourself an out on short trades (hedge in other words).
Otherwise get ready for the phone call.