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At 1.99 BTC, and a conservative estimate of 20M difficulty over the next year, it will take me 352 days to recoup the 1.99 BTC cost.
It difficulty averages 40M during that time, it will take two years to recoup your investment.
I love the bitcoin investment community, where a 2yr payback is considered terrible... Most investments are no-brainer good deals if the payback is under 10yrs, without lots of risk.
There's obviously plenty of exchange-rate risk with bitcoin, but who cares since these are fully denominated in btc.
The real risk is that difficulty rises faster than you assume, which I think is a distinct possibility.