It was hard to figure out how to remove a trace from a function. There's no mention in the trace-function, trace-function-background functions at all about the untrace-function and untrace-all.
The only hint about how to remove the trace is that it's advice, "This function generates trace advice for..." which isn't helpful enough.
You can reproduce this bug with these commands:
C-h f trace-function
C-h f trace-function-background
and notice the lack of mention of untrace-function and untrace-all.
Emacs version: GNU Emacs 24.1.1 (i686-pc-linux-gnu, GTK+ Version 2.24.12) of 2012-09-22 on panlong, modified by Debian
Operating system: Kubuntu
Thanks,