What has Facebook replaced?

Email? No
texting? No  Alternative instant messaging? Got rid of Some, but not a replacement.
Other Website? It has reduced the time people spend on them, but No.
What is it? The white pages. yes that is right. But of course that isn’t just facebook.  It is also your Contacts stored on your phone and computer. The use of mobile phones, and unlisted numbers has also risen dramatically. To a small extent also online white pages have replaced it.
Example: I know someone “always uses the phone book.” However that relative of mine would never call my home phone that was listed in the phone book.
What about yellow pages? they are still used some, but Google is the main company taking that away (even though yellow page companies partner with them).