Everyone has seen a 555 number in a movie or TV show. The FCC has declared a subset of those numbers for purely fictional uses. They did this so that real people wouldn’t be harassed by people dialing numbers they see in movies. Of course it isn’t perfect. Some producers don’t realize that only the 0100-0199 block of those 555 numbers are dedicated to fiction. Sometimes a tv show or movie, especially one from a smaller producer, will just toss 555 in front of a random 4 digit number and expect they are safe.
While the fictional phone number is an industry standard, there isn’t a similar standard for other communication mediums. Phones aren’t the only means of communication these days. People use email, Twitter, Facebook and other social media to communicate with one another. While a lot of shows will just make up a social media service to use in their fiction, a lot of them are near indistinguishable from their real life counterpart.