I live in the Colorado Rockies (Winter Park) and we had a Mountain Lion mortal attack several years ago in The nearby Rocky Mtn National Forest. A small child ran ahead of its parents and a cougar jumped him. Its good advice to keep the real little ones within a small perimeter of their parents when in the woods. This Lion was hunted and found to be diseased but regardless perhaps it could have been avoided if the group appeared to be larger by staying together.
FYI, I run everyday in the mountain trails and here is a few ideas I embrace :
A. Make noise. I clap my hands every once in a while and Occassionaly use a bear bell when I am very secluded in the higher altitudes. They are only $3.00 at REI and have a magnet in the carry pouch to stop the clapper when you no longer need it. This is especially important by streams where there is more background noise.
B. I carry a large can of bear repellent spray on the back of my Camelpak water backpack. I spoke to a hunter who has used this mace spray to ward off aggressive bears. Works on uncontrollable/aggressive dogs too.
C. No headphone,ipods etc. Be alert of your surroundings.