It's a risk yes, but I've been using it this way for about a year and encountered no problems.

I'm thinking of TIMTOWTDI, and that perhaps many people don't know about defadvice.

It's a little dangerous, but Emacs users have been making numbered backups automatically since before there was RCS. Since before there was GNU Emacs actually.

It is dangerous in theory, yeah. Much less so if you're a package like https://secure.wikimedia.org/wikipedia/en/wiki/Emacspeak which, while almost entirely defadvice from what I've heard, doesn't modify any existing state.

It is dangerous only if you change the function's interface.