http://www.coinwarz.com/cryptocurrency/?sha256hr=1000.00
IF these numbers are anywhere near accurate then it appears that at CURRENT difficulty you need about 60 days to make 1 BTC with 1 TH/s, so 3 months would give about 1.5 BTC - and the market maker at BFX is selling these for 2 BTC right now.
I guess if you expect the price to go down more than 1%/day then why not. These contracts are clearly overpriced right now. What is a bit scary here is where do these TH on the askside come from? Apparently a pool market maker. a) why would they sell their TH instead of mining? because they expect higher profit from it. b) do they have to sell if they see that there's a lot of shorts? with BTC you can get outside BTC in, if you have a mining rig then there is still no way to "deposit" TH into BFX right so the supply side is basically in the hands of 1 party. What is introduced to the market can be traded around but there is 1 party controlling the supply.
I also have a hard time understanding why a short would have to pay dividends, if there is actual TH behind this then that dividend should come from the pool and the borrower only pays interest.
If these were naked shorts of TH then there would be no pool to create dividend and the shorts would have to pay that dividend since they sold a contract with dividend of a TH. Shorts would NOT have to pay interest in this case since they would not be borrowing anything.
As I understand the announcement you pay interest & dividend if you short TH and that makes no sense to me.