I canceled my 5gh order at BFL lately because there is no point in waiting more than 3months for it. The difficulty is increasing at high speed. 5gh in 6 months will be nothing in term of power. As others stated... you would probably not be able to sell it.. and also can t switch it for litecoin mining. So it s a too big gamble i d not be willing to take at this point.

The value of bitcoin is another volatile value you can t determine to add in your calculation. Although you can estimate the futur hash rate increase and thus the difficulty.... you will not be able to know what a bitcoin will be worth tomorrow or in a year.

Too risky to me. Those willing to take the risk might get a lot of profit out of it... but can also lose a loy of money.