The biggest thing that makes me think twice about going for a ride is the safety factor. I, by necessity, ride alone 99% of the time. My two choices for riding (path vs road) each have pretty significant issues. The bike path nearest me is very secluded in some parts, runs through subsidized housing (think large groups of bored, disaffected and often angry young men rolling around on undersized bikes but not going anywhere), has easy access by other vehicles (service drives that aren't blocked off), increasing numbers of homeless men and so far has had two murder victims found on it. In addition my community is not bike-friendly. We have had multiple accidents most of them ending with a dead cyclist. It seems that drivers are actually aiming for us so the roads aren't a great option either. You'd never know that I live in a rather up-scale part of town.
The second thing is my personal discouragement whem I'm being passed by what appear to be 80 year old men on BSO's. Seriously, am I THAT slow!