It seems that people add everyone they've ever met as a friend on Facebook in order to keep in contact with them, but the problem is the resulting insincerity of it all. I called up Eric on his recent birthday, and he expressed irritation that so many people were coming out of the woodwork to wish him a happy birthday on Facebook. "I haven't talked with these people in months, and they just show up and post "happy birthday" on my wall." I remember the same thing happening to me, and frankly, I had the same reaction.
Insincere communication extends beyond social networking sites, of course. Speaking only from personal experience, many of the people I know who are in Campus Crusade for Christ have a tendency to neglect whatever friendship I may have with them, but if I happen to see one in the dining hall, the person will inevitably steer the conversation to probe me with very personal questions. It's so audacious as to be offensive!
Thankfully, the tendency toward insincerity is kept in check as a function of how peripheral the acquaintance is in my life. Eventually the person forgets my name and face, and can pass me on the street without recognition. On sites such as Facebook, however, there are no checks and balances. They might not remember what my name is, how they met me, or even what I look like, but when Facebook displays a little notification that it's my birthday, people rush in droves to plaster my wall with birthday greetings.
Please, make your communication's sincerity match the friendship's investment.