When I stumble upon an anime that I really like, I want to make it my mission to follow all the series offers closely. One of my pet peeves is getting interested in something and then missing out on elements that further the main story. The issue with this is that multiple anime series' offer new storyline content that comes from outside the anime.
The fact that these companies branch out and offer new content via other mediums is not a bad thing. It just makes it tougher for fans to really keep tabs on what's happening. When you have to take in 10 different types of content to stay on-top of a franchise, things can get very hectic.
Usually it all starts off with a manga. When that becomes popular enough, the translation to anime begins. When that step of the process is a success, the sky is the limit. This can lead to more manga, a movie, video game adaptations, light novels and much more. All this content coming out can make your head spin, and if you miss one of those elements you might miss a new/interesting/important story element!
How do you keep tabs on your favorite franchises? Say for example, One Piece. Do you read all the manga, watch the entire series, play the games and more? Is there just too much content and too many avenues for you to stay completely in the loop?