I just accepted a bid. I did use Black-Sholes to check that the bid was reasonable, the problem is working out what kind of volatility to use. Current volatility is lower than historical volatility. So it depends on what you believe about the future volatility of bitcoin. My view is that past volatility is more to do with Gox than bitcoin and Gox is gone thankfully.

Also the trade was purely trust based (offered escrow but for the amounts involved the buyer was unconcerned). In the long term this is the only way any business can be sustained. Look at services like "spendbitcoins" he has been going since very early days and never ripped anyone off. I would be confident to make a million dollar trade with him because of his record. I would be willing to take the risk of a small trade with someone new to see where it goes and in that fashion one can build trust over time. Any scam involving options can only last until someone tries to exercise. So as long as people are trading relatively short dated contracts a scam would not be able to be sustained. The main issue is the risk that an option writer dies or goes broke and that is where collateral and escrow will become important.