Sending Messages to Non-Friends on Facebook
You can message a person who is on Facebook even if they're not a friend (if that person’s privacy settings allow it). This is particularly helpful when you encounter someone on Facebook whom you’d like to say something to, but are not sure whether you want to add her as a friend. Here are a few examples:
Identification: Say you search for an old friend and find three people with the same name. One Profile has a clear picture of someone who is definitely not your friend. The second person is in the Dallas network, and you’re sure your friend has never lived in Dallas. The third Profile doesn’t have a picture, just a placeholder silhouette. From the search results page, you can click Send Message next to the person with the placeholder Profile picture and ask whether you know each other.
Friend of a friend: For most features on Facebook, you need to be someone’s friend or at least in someone’s network in order to interact with them in any meaningful way. However, sometimes you have legitimate reasons to contact someone who really doesn’t belong on your Friend List. For these interactions, Facebook messaging is perfect.
Getting to know you: Pretend you’ve just joined a new company and you know very few people. Or to really experience this example, go join a new company. You can use Search to find other people at the company whom you’d like to get to know or ask a question, and send them a message on Facebook.
Messaging a non-friend should be treated with caution. If you message non-friends too often, or too many people report your message as unsolicited or unwanted, your account is automatically flagged by Facebook. People who send too many unsolicited messages may have their accounts blocked or permanently disabled. If every person on Facebook could message everyone else, Inboxes would start to fill with impersonal or unwanted messages, eventually making the Inbox too messy to be functional.