What difference does it make? People are used to weird errors, so it doesn't scare away "normal people" anymore than a fail whale would. People trying to break the code are not aided much by one filename and line number, either.
It's annoying to look at, and I wouldn't do it... but it doesn't really matter.
It's just a show of a lack of professionalism. I view exposing low-level errors as akin to spelling mistakes, typos, poor photo work, and other symptoms that show the content producers just didn't take the extra step to differentiate from amateurs.
I hate to beat the cliche, but just one of the reasons I feel happy when using most of Apple's products: they just scream that even the details were very much thought about.
Except the time my iPhone went into Chinese-language panic mode and started warning me that something completely arcane was happening and would only shut down after I took out the SIM.
There's a removable SIM caddy at the top that can be popped open with a paperclip or a key included in the iPhone 3G packaging. It's the battery that can't be easily removed.
It's annoying to look at, and I wouldn't do it... but it doesn't really matter.