Robert Maxwell wrote:
The payout is already a fraction of what it used to be. It takes exponentially more power to mine now than it did when Bitcoin started. It's already to the point where it is not practical for individuals to mine anymore, unless they have massive hardware on which to do it. Otherwise, people have to pool, or they completely waste all the cycles they spend mining.
If that's the case, then it probably isn't feasible to do at a large scale either. It was always iffy as to whether or not you could make enough BTCs to break even on electricity and hardware. We've probably gone way past that point already.
Sidenote: THIS ARTICLE
that I pulled up while trying to figure out how well BTC mining scales is probably the best layman explanation of a CPU and GPU I've ever read. They break it down very well.