I'm trying to look at it from both sides. What we know is Jason "allegedly" knew a guy that ran a book and he was being the middle man placing/relaying bets for Chris.
Now if the bookies name was irrelevant to Chris Moneymaker at the time he got involved with this in the first place then Chris was being too trustworthy and naive about it all. Chris was willing to place bets through Jason to this bookie without the bookies name so he's putting his faith in a guy on the internet kind of like other people have in the past including here on PFA (tough but fair regarding Jasep).
I'm not saying any of this stuff is right or justifies a reasoning to do something a certain way but Moneymaker has shown tendencies to be very naive in this situation not caring enough to demand that name himself even if it's just a nickname when starting out so he's guilty to a fault especially when Chris has been betting for years.
Chris states he's been stiffed multiple times (he rolled some himself too) so whenever that happens to you in life shouldn't you be more protective of yourself not to get rolled again by getting as much information as possible? Well, he didn't because Chris was more desperate to place some bets then care about that at the time.