Trail Run Hydration

I guess it depends on the length of trail run, weather and if there are any aid stations.  If it was a 5 mile trail run with temps that weren't all that hot I wouldn't bother.  When I did a trail marathon last year I used it as aid stations were between 4 and 7 miles apart, so I carried my water and nutrition and felt it was necessary, but would eat and drink some of the offerings at the aid stations.  Some of the longer trail runs require runners to carry something for hydration and I find the Camelbak on my waste is mush easier then a handheld water bottle, but that's actually what a majority of the runners seemed to use at the trail mary I did and a good chunk of those folks were actually doing the 50 miler so it worked for them.  I just don't like carrying things in my hand.

REI has a lot of different hydration systems thou you may be able to find prices cheaper elsewhere:  http://www.rei.com/category/4500188

I forgot to mention the Amphipod bottles, it's a great combo.   I added two Pods to my Camelbak and carry Infinit for my nutrition on long runs.