Quote Originally Posted by Cannibal View Post
Bear spray: Pretty much useless with an aggressive bear, particularly if it has been sprayed before. Pepper spray works once, from what I've been told by a lot of backcountry folks while living in Colorado.
Bear spray is intended for aggressive bears.

As for its ineffectiveness on bears that have been sprayed before chalk that up to urban...er...rural legend. It's extremely unlikely that that any bear involved in an aggressive encounter could be identified as being sprayed before. On the other hand, there has been some controlled/captive testing. I don't know but it seems logical that the captive bears were subjected to repeated tests/sprays.