Looking at the DBFS website, bear canisters are recommended, but they don't appear to be mandatory. Hanging food (at whatever recommended lengths) is a technique that works for less sophisticated ursines that have not passed Food Procurement 101. Sierra Bears all have doctorates in that field and are continuing with advanced research.
OR, yes, the rules were put in place in the DBNF following a bear attack. The first ever reported in recent history in KY, in 2010.
These rules are pretty much the same as any other area with bears..
Do Not Feed Bears
Do Not Store Food in Tents
Do Not Burn or Bury Trash
Do Put Trash in Bear Resistant Cans
Do Store Food in Cars (I guesss the forest service should consult the video's of bears opening cars like tuna cans to get food)
Do hang your food 10 feet high and 4 feet out from the trunk of a tree.
The DB National Forest put these rules in place because of a bear attack, and to keep the bears natuarally afraid of humans.http://www.fs.fed.us/r8/boone/
I stand corrected. I mentioned in an earlier post that there has never been a reported bear attack incident in the DBNF.
I do have friends in the far eastern corner (Hatfield and McCoy territory) who are seeing bears on a fairly "regular" basis. Not sure if they're seeing the same bears multiple times, but I do know we got a heck of a spike in bears over the last 20 - 30 years, and backpackers not used to dealing with them are going to have to get used to them, and how to deal with them.