This is not a new thing.
A long, long time ago, I went to see a new movie, that I'd heard nothing about. It was sci-fi, and I was expecting (possibly) something similar to "Alien", which I'd seen recently. That movie was "E.T". The movie is 100% better, if you have no idea what E.T. looks like, or if he's good or bad. You don't even get a glimpse of him for a good 30 minutes or so (it's actually pretty creepy up until his nature is revealed to Drew Barrymore). I am one of the very few people who have seen that movie as it was meant to be seen, just because I saw it that first weekend it came out.
Perhaps not a new thing, but now I can go online and immediately see someone posting spoilers to a TV on Facebook. Other times I'll see headlines from a site telling me exactly what was leaked from XYZ productions. Much more likely to happen than me being unable to hush up my talking friend before they give away the ending to something.