In general, I would advise something more powerful than 9mm for bears, too. However, in practice it has been more effective than I would have thought:
Discussion
Interesting read. I wouldn't want to test the theory irl. Another interesting note from the article is carrying FMJ rounds (which I rarely do.) You would have to get some seriously lucky shots to penetrate a vital organ on a fast moving Bear before it mauls you. No doubt a magazine dump will do the job eventually, just not fast enough.
Absolutely. I am still recommending magnums for hiking in bear country, for sure.