I'm not sure -- so many business and job opportunities come via word of mouth and personal recommendations. At times in my life when I have been more social, I've had a lot more opportunities than I do when I seclude myself. Even just really basic stuff -- my fridge stopped working. A friend happened to be moving and sold me her one year old fridge for practically nothing.

I am probably thinking more of acquaintances than friends, though -- just knowing a lot of people seems to make life easier when you want to find a new job, start a business, produce a play, have an art show, etc.