I bike solo all the time. Since moving to AZ I have really increased my distance on rides. I have been from Phoenix to Wickenburg and back 4 times, have been to black canyon city multiple times and took a 180 mile round trip to Camp Verde and back.
Again, like hiking, I prefer to bike solo because you don't have to worry that the people you are with will wimp out on you and want to turn around. I am the type that likes to go as far as possible on hikes and rides to escape the 'concrete jungle'.