I see three ways we are all imapacted by Facebook...
You may be missing out on deep friendships if your social plans are made solely on Facebook.
If you organize an event and invite your Facebook friends, 20% of your friends may never see it. Make sure you figure out a plan to stay connected to friends, family and customers who will never be on Facebook.
If, like me, you only put parts of your life in Facebook, give thought to how that might be misunderstood.
For me, I show lots of stuff about work, but very little with my family, due to my wife's desire to stay off of Facebook. Does this make me a workaholic? Well, occassionally I am, but this image is definitely exaggerated by the type of content I post (and more importantly, the content I DON'T post) on Facebook.
Everybody should recognize that there may be more dimensions to some of the friends you connect with than what you see on their Facebook page.
If you aren't on the site at all, that's fine! But you need to be twice as intentional about building offline relationships.
Remember that Facebook is a convenience for two-thirds of your friends, so they may be prone to overlook you. Reach out to friends and make plans... don't let Facebook make you feel like an outsider.