Yes, it'd take somewhat more than one line of C++ code, at least to do it right. the biggest problem I see is that all clients would be requesting the MtGox API data all the time, resulting in possible DDoS. Also, it should be an option, because not everyone might want reveal to MtGox that they are running bitcoin...

Also, MtGox is only one of the exchanges, and people will probably want quotes for other currencies than the USD as well.

I wonder if there is some more efficient way of distributing the exchange real-time quote information that doesn't involve polling all of them all the time...