[hughpeters]

Wow! Thanks for all the replies. Glad other people found this silly idea interesting.

A lot of the issues that were brought up have to do with fees associated with purchasing all the stocks and the fact that you would have to buy very small fractional shares. Certainly big issues today but they don't sound like showstopper problems to me.

And to the folks criticizing my lazy use of the term "open source" - I apologize. I should know better using that phrase on hacker news!

To clarify: clearly the market weighted index process is a well known and very simple algorithm. What I meant by "open source" was a tool that can employ that market weighting process and handle all of the financial transactions necessary to execute all of the trades.