Interesting question. The book was published in 1985, far before the days of Facebook, but actually even before the days of the Internet as we know it (which was launched for public use in 1992). I always found it particularly interesting when Ender was at school at the very beginning of the novel, how each student had his own desk and uploaded files at the end of the school day to be checked at home. Even before the Internet, Card had an idea of a system of communicating via computers.
All of the students at Battle School have desks (which I picture to be similar to over-sized iPads) and log on names. They can send messages to other desks, similar to instant messenger. They can hack into each others files and "trash" the security. All of these ideas were very technologically progressive for the time the book was published, but of course, by today's technological standards, they are commonplace.
Though the kids in Battle School do not have any contact with home, we know that some how the Mind Game has access to information and records that are up to date and can go back and forth between Earth and the Battle School. This was shown when an age appropriate picture of Peter appears in Ender's journey through the game. Again, though it goes unexplained, to a modern audience the idea isn't so far fetched. We are used to the ability to obtain information and photos from remote access points, via again, the Internet.
Finally, the letter Graff has Valentine write to Ender when he seems stuck in his training (chapter 9) appears when he signs on to his desk as "Mail Waiting." This seems pretty similar to email. Teachers or other authorities in the school can contact any student immediately if he or she is signed on to a desk and the message will simply appear on the screen (ie: "Report to commander immediately. You are late. Code Green Green Brown.")
The social media of Ender's Game compared to today is strikingly similar. I think the differences are mainly in the details, which, for the most part, are left out of the story. One thing you might note is that there does not seem to be the use of telephones nor video for communication in the book, as we have today. And, of course, the "how" behind communication is mostly left out of the book. Fascinating though, how far we've come since the novel was first published.