"Even if he starts with the absolute minimum bet, he could still run out of money after losing thirty, fifty, a hundred times or more in a row. "
If the site you're gambling at gives you a 30 loss streak in less than 1 million rolls it is rigged.
*facepalm* It is irrelevant the size of the losing streak - it does not prove that a casino is rigged, only that variance thus far has been a huge dick to you. To prove something is rigged you actually need to find a piece of code that is changing the outcome of your rolls such that you lose, until then the best you can say is that the site is extremely suspicious.
How about getting 30 loss streaks multiple times within a week (at 49.5%)? Would you consider that dice site rigged?