I’ve found Facebook to be a tool for getting good face time for service organizations and groups to interact among themselves, or with the public. I maintain two service organization pages that allow interaction within the group, as well as publicize what we’re doing. I also belong to a closed group of former employees of a defunct company, that allows us to get together and reminisce, share stories, and keep up with one another.
For this, I find Facebook worthwhile. OTOH, from a personal standpoint, I spend no time posting errant thoughts or playing stupid games.
I enjoy facebook, but like many things in this life, it can be a big waste of time (no different than people who golf their lives away). Facebook is pretty invasive though, so I imagine some other thing will eventually surpass it.