Sports: I bought my first DVR specifically to record the 2006 World Cup games while at work. I was in my first few months and did not feel like I could afford to take off work to catch all the games I desired. For the 2010, I tuned out of Facebook because I knew lots of people posting live about games. Comments by friends on social media during a game is usually better than the announcers. Unless someone I know is actively posting about a game, I tend not to post anything of my own trying to respect others who might be time shifting the game.
Books and Movies: If asked, I tend to spoil books and movies. I tend to be better about holding myself back for movies newly in theaters or on DVD/Bluray. But if something has been out for a long time, then someone has had plenty of time to consume that story. Maybe they eventually will, but I tend not to save up things. Probably because the longer I wait the less likely I ever will. The exceptions for me tend to be the movie version of books where I watch after reading. The difficulty for me is explaining why someone would or would not want to see something with them feeling like it has not been spoiled.
George R. R. Martin killing off the sympathetic characters is a good example. Some people hate it. Some people love it. It feels unfair not to warn people that it happens in each book. Why someone might like the TV series better without saying anything that happens? Ugh.
Scripted Television: Pretty much both issues of sports and movies apply. I am not very sympathetic regarding shows that have been around for a long time. But I try not to spoil things that are live.
So, I guess people should avoid talking about things they want to see or read around me.