One of the best things about Facebook is the ease to find old friends.
More than a year ago, I located an old friend, having not seen in over 20 years.
I was at that time having a work problem and he alerted me to a contact of his that had the exact experience to help me and thus saved my job. I was stuck in a project and had passed the dealine already.
So while it is true, that it can be a time waster, it also has been very beneficial to me.
One way to avoid wasting time, is to not post that much of your own inyanim. This will cut down alot.