This is a link to today’s TV Club Classic review of Scrubs. In it, the reviewer points out his frustration with how TV reporting is done nowadays, which allows for rampant spoilers.
Most sources of information for entertainment (McNutt specifically points to Entertainment Weekly’s Michael Ausiello) will report on shows hiring guest stars to appear on multi-episode arcs. This can be exciting, learning that a great actor will appear on our favorite show, but is also has the unfortunate result of telling us how long this person will be around. Therefore, if we know that a specific actor will appear in four episodes, when his or her character is put in mortal peril in his or her first episode, there is no tension, because the character is nearly guaranteed survival. (Only a select few shows can get around this; it’s not outside of the realm of possibility to imagine The Vampire Diaries introducing a new guest star as a human, then making him or her a vampire for the remainder of his or her arc.) But even then, we know that the character won’t stay dead for at least a few more episodes, and we know that he or she will leave at a certain point. We know that the character won’t become recurring until new episodes are filmed, if at all.
Another problem, which McNutt doesn’t allude to specifically (he was more focused on the issue addressed in the previous paragraph), is episode-by-episode press releases. I remember back when I was watching LOST, the releases submitted by ABC would state which actors were going to guest star in each episode. If the actor played a recurring character on the show, it was pretty easy to guess what the episode would be about. For example, if Marshal Mars was set to appear, it was almost certainly a Kate episode, whereas the appearance of Penny usually signaled a Desmond episode. This isn’t as bad as the first problem, but sometimes revealing that a character will show up will ruin the surprise, especially if the character has been away for an extended period of time or was assumed dead. I’m nearly certain that Christian Kane was left off the release for the Angel episode “Destiny” for this very purpose: the reappearance of Lindsey was the episode’s twist.