There's a hilarious episode of The IT Crowd in which the three main characters join a social networking site called "Friendface" and end up as social outcasts, feverishly clacking away on their computer keyboards to communicate with one another online rather than in person, even while sitting in the same room. So, yes, sometimes technology can isolate us.
However, my brother told me today during our phone call that a couple of weeks ago he posted his address on Facebook along with a plea for letters, which he meant as a sort of joke. About 10 days later, though, he was very surprised to find two letters from old high school friends in his mailbox. Now, my brother currently lives in Tasmania, so that means these old friends of his, whom he hasn't seen in years, saw his Facebook post and almost immediately wrote, stamped and mailed their letters, which then had about a 10-day journey from the U.S. to this Australian island state.
I'd call it a definite case of technology helping to alleviate isolation rather than cause it. Of course, it does take a human hand to actually write, stamp, mail and deliver those letters.