Use names of real social media websites or make one up for story?

[Shannon Petruchio]

It probably doesn't matter. But when I think about networks like mIRC, that no one uses anymore and probably most people have never heard of, if I published a book back when that was actually a thing and referenced it, the reference would be lost on today's readers, at the same time to explain something like facebook could seem completely condescending to the reader. So while you can do it, it might be better to just make something up.