Maidak,
This is interesting; I just went and purchased some of the FHM and the FHA contracts and see how these play out, hell I might have to stop buying gear and let other people mine for me and they can maintain the gear
So much like the stock market with futures.
I have done a lot of different gear including (and I'm probably missing a few) plenty of Avalon, BFL (FPGA/ASICs), cairnsmore1 (look it up loved the design - hated the serial interface - flaky!), KNC, Chilis, Klondike, AsicMiner, BitMain, LTCgear, and have won and lost on some of these orders like many others here and almost cried (And rejoiced at KNC shipping the first round so promptly). I can totally see the point of buying just hashing power on an exchange, then letting it mine to the point you sell at a lower cost, your 3 major data points I see in this (and I'm probably missing many) :
1. Will BTC be higher or lower (but then again if you just held the BTC does it matter)?
2. How high will the difficulty be?
3. At what price did I enter into the GH contract, and at what price can I exit the GH contract, and how much BTC did I make in the middle before I exited.
I personally have ~2Th at Ghash.IO, ~1TH at Slush, and ~1TH at eligius. Figured to play the lottery across few pools. I also bought some GH at Ghash many many months ago and leave it there for extra BTC generated.
--iLuvPCs
This is interesting; I just went and purchased some of the FHM and the FHA contracts and see how these play out, hell I might have to stop buying gear and let other people mine for me and they can maintain the gear
So much like the stock market with futures.I have done a lot of different gear including (and I'm probably missing a few) plenty of Avalon, BFL (FPGA/ASICs), cairnsmore1 (look it up loved the design - hated the serial interface - flaky!), KNC, Chilis, Klondike, AsicMiner, BitMain, LTCgear, and have won and lost on some of these orders like many others here and almost cried (And rejoiced at KNC shipping the first round so promptly). I can totally see the point of buying just hashing power on an exchange, then letting it mine to the point you sell at a lower cost, your 3 major data points I see in this (and I'm probably missing many) :
1. Will BTC be higher or lower (but then again if you just held the BTC does it matter)?
2. How high will the difficulty be?
3. At what price did I enter into the GH contract, and at what price can I exit the GH contract, and how much BTC did I make in the middle before I exited.
I personally have ~2Th at Ghash.IO, ~1TH at Slush, and ~1TH at eligius. Figured to play the lottery across few pools. I also bought some GH at Ghash many many months ago and leave it there for extra BTC generated.
--iLuvPCs
A wise man once told me never keep all your eggs in one basket.
So spreading the mining power across multiple pools is a very good tactic! 
