Should Python raise a warning for mutable default arguments?

[Emile van Sebille]

Dan wrote:
> I'd suggest that at the 
> end of the tutorial, when people have a better general idea of how 
> Python works, there would be a Python Gotchas section.
> 

Hmmm, OK -- mutable defaults, integer division, name mangling...

I'd think decimal precision is more a general problem than a python 
problem, but still one that throws newbies...

Any other ideas for gotcha's (as opposed to faqs)?

Emile