As a writer of novels I have a pretty good grasp of the creative process that happens when one person works on a story, works with characters, changes the world and tries to make it right. I'm lucky because I get to write the entire thing then go back and edit it to figure out what doesn't work. I get to smooth it out and add or remove bits and pieces of plot that otherwise would wreck the flow of the story.
Writers of television shows apparently must collaborate with a bunch of other people for each storyline. Also, they might have a few shows written, shot, and released before they know exactly where they're going with the season arc (if there is a season arc.) I can't imagine being in this situation and staying sane. Considering how attentive good fans can be (and going by some of the trivia posted here in TV.com, some fans are damned attentive) it's impossible not to screw up here and there. And they'll be watching your every move.
Last season's writers' strike had a lot of shows finishing up in places they never intended to go. Bones is a good example. It's been said that the grand finale of Zack being Gormogon's apprentice was pulled out of the air to give the season an exciting ending. Many of the fans were not impresed. Not only did the whole thing seem out of character for Zack, with almost no lead-up to the reveal, but fans didn't want to lose the character. It was a cheat.
This season's first few episodes show that the writers may be trying to make up for that by placing new reasons/excuses/changes to last year's events. Whether it will end up feeling justified or contrived will be revealed as the season goes on, by fan reaction.
Some shows tie in to just one person's vision of the story, and I think they benefit from that. J. Michael Straczynski imagined Babylon 5 as a five year arc, and that worked even though it was almost cancelled and then renewed at the end of season 4. Joss Whedon has been rumoured to plan well in advance, and finding details placed years before the payoff is a good passtime for those who have seen all of Buffy the Vampire Slayer ten times over. And Eric Kripke, creator of Supernatural, is on record as saying he has a five year plan. There are still a lot of writers and imaginations contributing to the stories so I'm not trying to take away credit where credit is due. But the fact that there is a unified vision of some sort is a plus, I feel. At least, it is in my experience.
Or maybe I just don't work very well with others.