Anita,
There may be good reasons for an individual to not participate in social media. For example, previous or on-going work in the criminal justice area may expose a person or family members to risks that are avoidable. I am sure you can think of other sensitive areas (medical, political office, etc) for which it is not prudent to expose personal information. I do understand (and distrust) promises of limited exposure to data of the users choice...recent history has shown these promises to be unreliable.
I have such personal reasons to avoid facebook and other such social media. Please take these facts into account when you promote/urge folks to join facebook. The advantages do not necessarily outweigh the benefits for all.
Regards. Dick Green