There are certainly many potentially dangerous situations backpacking into the Sierra Nevada though one can easily avoid almost all of them by planning an easy and gentle trip. For new backpackers there are certainly many unknowns likely lurking in their minds that no amount of studying how to books or talking to other experienced people is going to calm until they actually get out in the backcountry and work through some experiences. And I would guess the fear is greatest solo and less so as a group size increases. For those who already spend time hiking in our mountains, the transition from hiking to backpacking may be trivial. For the urban person that is just experiencing the mountains it may be significant.
The greatest fear for most people rises during nights when people for the first time have to face the primal human fear of wild animals, particularly bears.
At lower elevations the same situation occurs with mountain lions. I don't thnk most people really expect beforehand to be so afraid
until they are actually out there on that first night at a remote place and suddenly they notice how creepy it all is unlike anything they have felt.
My suspicion is there are numbers of new backpackers that never backpack again if they have a night time bear experience. Such is far more scary for the solo person camped remotely. Especially in a dark tall mid elevation forest where every night time critter walking about causes crunching twig sounds. All sorts of spooky noises. Worse for those sleeping outside without a tent where one feels...EXPOSED.
And even if a person has heard that their particular area has not seen any bears for years, it won't make much difference as their heart goes LUB-DUB LUB-DUB LUB-DUB LUB-DUB
About then the new backpacker is fumbling about in inky blackness inside their tent for the one flashlight they brought along. Dang? Where is it? They furiously feel all over, in their pockets, beside their sleeping bag, but it isn't anywhere so they start over and it still taint. Is it in my pack outside by that tree? They grope for their tent zipper but the notion of opening the door is daunting. By then their fear is compounded by a loss of control. Finally the person gropes about into the back end of their tent where they find the little tube rolling loose. And on goes the light Whew! But then crunch cruch...what's that noise...LUB-DUB LUB-DUB LUB-DUB LUB-DUB