My team just had an coworker leave for another team. This coworker was very smart, very hardworking, and very dedicated. But he continually chafed against any sort of documentation or communication. He also chafed against any established standards or policies; pretty much did what he wanted, and was never really called on the mat for these issues.
He got away with this because he was a "rockstar." He could solve some pretty hairy problems fairly quickly. But explaining these fixes to others was difficult for him, and many of his solutions were MacGyver-esqe. He had come from a small shop where he wore many hats; we're a large enterprise with lots of teams. This means that communication is probably the most vital skill for team success.
Since he didn't share or document his changes and fixes, the remaining team members are now left trying to divine what he did. While I blame him for a lot of this behavior, I primarily blame his manager who continually tolerated it. Ironically, this manager is shocked and confused as to why he lost his rockstar.