The change in difficulty is a HUGE unknown variable in ROI calculations...as is the value of the bitcoin itself.
Would I advise somebody to drop $100k on a mining setup? Only if it's clear they have the ability to move $100k worth of used computers if they needed to.
It would feel the true opportunity in bitcoins is meta....an exchange, a service to facilitate purchasing of goods from sites that don't accept bitcoins, etc. It "feels" like this is an emerging market with many opportunities...but I feel like mining is small thinking, in terms of generating significant recurring revenue.
Great points. What would an example of BIGGER thinking, in terms of generating significant recurring revenue using bitcoin as a platform or utilizing it another way?