I think part of the reason they consider he is "betting" or "risking" his fortune, is because it probably has a lot more risks than a "simple investment". i.e.

I think part of the reason they consider he is "betting" or "risking" his fortune, is because it probably has a lot more risks than a "simple investment". i.e. he's not taking his money and putting it in a Fidelity investment account, he's spending money to create a game that might very well not sell more than a few copies and not make the money back. I guess people see him as "winning the lottery" with Braid, so now spending that "lottery money" is seen as a foolish move. However I think that spending/investing your hard-earned money in something you enjoy (developing games) is the best investment one can do, even if you do lose all your money.