I worry that the difficulty level will increase to such a point BEFORE this project even gets started that it will make the whole venture uneconomical. Remember that you're chasing a MOVING target - the difficulty level. At some point the amount of money the investor will be making from his share of the rigs won't be enough to cover the cost of the administrative fees or whatever he will be charging.

This is the same scenario with minim on our own (non cluster) except if we do this on our own eventually down the road when the difficulty level is too high to keep our rigs mining we can just SELL our rigs and get some cash back. I don't know how we'd have that option in a mining cluster. I suppose we can sell our shares on the newly proposed stock market, but umm what if nobody wants to buy your shares - and you can bet they will not if they know that it will cost them more in electricity/administrative fees then they get back in BTC.

Please don't misunderstand me as trying to throw a "money wrench" in this venture. It's just that there are a few unanswered questions that need to be addressed.