For some it's really not that easy. Paul Miller's article about leaving the internet for a full year is pretty interesting, and touches on some important aspects of social networking. Facebook enables casual long distance relationships that are often not realistic for many of us. I rarely talk to my best friend from high school on the phone or via text, but we do interact via Facebook pretty frequently. Without that social network link, we would've fallen out of touch over the years - with it, we're able to stay relatively up to date with minimal effort.
Now, do my friends deserve *more* than minimal effort? Of course. But the reality of leaving one's hometown (or college town or longtime employer) makes it unlikely that I'm going to see/call/write those friends of mine on a regular enough basis to keep close connections going, something Facebook has made possible for me.
For those of us with (even mildly) busy lives who have met many wonderful people over the years, social networking has been terribly useful.