I'm looking into signing up for a year contract on one of the cloud mining sites. However, I'm concerned about the increasing difficulty over time at the locked Gh/s. In what ways can I calculate the loss I would face over time as the difficulty increases?
Unfortunately Mining is a zero-sum game for the average individual at this point. If you sit and honestly think about it, who would sell a machine which literally generates profitable revenue after expenses? If you are planning to invest in the Bitcoin domain than I would highly recommend just obtaining Bitcoin and storing it in an offline wallet. This has proven to be the most profitable strategy thus far. Take for instance all the disgruntled miners who were delayed for over a year on receiving their hardware. Once they finally received their hardware it was obsolete and wouldn't even generate a profit versus electricity if being ran. Every single one of those miners wish they would've just saved their money and purchased or held Bitcoin.
If you are still curious or just interested in mining, then I suggest checking out CEX. They seem to be a longstanding and reputable company as far as the Bitcoin world goes. There has been an increase in scams lately which portray "profitable" virtual mining contracts, so please be aware of any "too good to be true" deals.
If you are asking how fast is the network growing, it is hard to tell. Many people try to give estimates on the network hashrate and only seem to be correct by coincidence. However looking throughout the history of bitcoin, with exception almost only during periods following huge price increases, one would get more coins for a certain sum of fiat than if they invested said sum in mining equipment, not considering labor, replacement, and power costs.
By getting a cloudminer, you are essentially paying all these costs up front to a company who promises they will take care of this for you.
This is not to say that mining is not profitable or a good investment. If you have your own miner, you have equipment which maintains some value over time (you can sell old rigs to pay for new). Mining is a serious endeavor, and miners are appropriately named by some "the bitcoin working class".
This has evolved to the next level with bitcoin and ASICs. You need an engineering degree to build competitive bitcoin mining rigs. However litecoin and other alt-coins are still fair game.
If you would like to learn more about how computers work on the hardware level, I would suggest building your own rig with 1 or 2 GPU to start. If you believe in the long term success of crypto currency, then now would be a good time to buy a rig (many desperate people are panic selling their equipment).
Else, buy bitcoin.
Ltcgear has a concept of multiplication to offset difficulty increases. This really helps to keep payouts the same. Not to mention they have the best price per mh and have been running with no issues for over a year. http://ltcgear.com?apage=1150