It's a great idea in theory but at this stage I think it's hard to implement properly. It's still a bit early to tell which coins to include, how to settle discrepancies, caps, rebalancing, etc. And most of all, who to trust to handle the whole thing.

Of course, there are many who will step up and volunteer to run such an operation. There's talk of establishing an ETF so how far away can an index be realistically? But the real question is, how secure is it if it's not centrally regulated, and on the other hand, do we really want any central regulation interference in here?