I truly believe 'alone' is more a state of mind than anything else.
Having recently left a veritable 'Office-Space' like enterprise, with 500 people on my floor you'd think I wouldn't have been so lonely. But being lost in a sea of cubes and water cooler/misery loves company talk replete with excuses of why someone can't do something and something didn't get done at every corner can wear one down.
As a newly minted Rails consultant going on 6+ mos now, I have yet to meet any of my clients/designers face to face (there's 10 people involved in 2 separate long term projects). They live on the East Coast and I'm in southern California. But we're in regular communication... skype/google hangouts, phone, basecamp, email, pivotal tracker, github.
When it comes to my career I'm feeling amazingly whole when I'm 'virtually' surrounded with highly competent people who see eye-to-eye than when I had to grudgingly come into a mediocracy every day. I've never experienced this level of cohesive team work before... to me it just seems like the physical presence thing is icing on the cake.
If I get 'physically lonely' heck while working I'll go out to one of various local cafes I frequent and take my headphones out every once in awhile and chat up a stranger. Usually we have far more in common than I did with any of my former co-workers. To top it off I find myself more regularly hanging out with friends while not working... having a fluid schedule + getting rid of that time sink that is commuting really opens up one's options to be social.