What!? Throwing myself thru trees and over rocks out in the middle of nowhere ALONE is dangerous? But then I'd have to meet new people and be social... oh, wait... I like meeting new people and being social. Almost as much as I love mtb'ing.
Salmon Falls, Granite Bay, Auburn, Cronin, Del Paso, Secret Ravine, Rockville, Skyline, Pioneer, HITG, D-Ville, Oat Hill Mine, South Yuba, Sly Park, China Camp, Annadale, North*, Mammoth, Sawtooth, Black Rock AZ, Santa Cruz, Tahoe Rim Trail, Lake Oroville, Mtb Oregon, Coyote Ridge, Capitol Forest.
My favorite trails are heavily wooded and are all about FLOW (Connector in Auburn is a great example). I want to explore more of the Sierra, Bay Area, and northern foothills, as well as unknowns close to home.
To meet new riding partners with a similar fitness level. This will get me out riding more and ultimately insure a level of safety that I can't get while riding alone. The fitness may end up being negated by the occasional post ride beers, though.
YES
Come out and meet some new people and learn something new about riding your bike!