1. Bitcoin can fail anytime (see the thread about a google competitor) and electricity prices aren't the same worldwide.
Very true. But if someone steals Bitcoin and starts a new block chain, then I'm already equipped to take my mining there too. And I will be there on the ground floor, instead of two years into it.
2. I don't see hwo they can be worth 0.57USD when the market price is way above.
That's me being conservative. I think BTC are overvalued in the short term. 0.57 comes from ignoring the huge recent hump in the overall growth chart. If I am wrong, and BTC are really worth more, then mining is even MORE profitable.
I believe if anyone has a heap of $$$ to bring to the table, and they want a more reliable return, they will be reading this board first, and they'd be nuts not to throw it at MINING right now. The ONLY thing that will make the value at MtGox rise, is someone bringing moneybags to MtGox, and nothing else. By making posts and presenting evidence like this, I am very arguably preventing that from happening, singlehandedly.
3. I just can't estimate the growth in difficutly, there could be a jump-in or a jump-out of huge computation power anytime.
You are absolutely right. Mining controls for that though. If there's a huge jump-out, mining will produce more BTC per miner. Isn't that good? That would make mining either the same profitability, or MORE profitable.
4. If you need the cards for other stuff than mining, you maybe do.
Maybe. but I have made the conservative assumption that I don't. If I do, I'm profitable faster, since instead of a $2000 outlay in equipment, I am only paying its depreciation, which is MUCH less. So, in other words, if I'm wrong, mining is even MORE profitable.