Zombies should never run. I reason it like this - they're dead so stumbling etc should fit in with how they move. Dealing with rigor mortis etc stiff limbs I can't imagine them to be able to run and it ruins the suspension of disbelief for me. Now maybe the amount of time they are dead should factor in. If they just died and turned into a zombie they should be quicker than the zombies who've been dead for a week, a month, a year etc. It just never felt right for me having them move too quick. It's not the same as say Vampires where that form of being dead isn't the same as zombies. Zombies should have all the characteristics of dead bodies with the exceptions of them being able to move and eat/attack people.
It's interesting that nobody has ever come clean about what happened with Frank Darabont. Even though season 2 was great there was that lull when looking for the little girl which felt like it took forever and then Lori's inconsistency about Rick and Shane was nerve-wrecking. I hear he had issues with AMC executives (damn executives always have to mess with the good shows) over budget and other issues. Of course Kirkman can't comment on that because of putting the show in danger. I would have to think Darabont would have prevented both problems during season 2. Also interesting to note that Kirkman has an ending in sight even if it is a long way off. Before he mentioned that it would probably never end (like he is now saying about Invincible). I couldn't see anybody else writing The Walking Dead (comic that is) and Kirkman's involvment in the TV show comes through as the characters reflect themselves from the comics even though there are some major changes the spirit of his work is there which is how it should be. I just hope they play up the isolation of the prison because while it does become a sanctuary for Rick and the group it also becomes a sort of prison as well often trapping them inside when zombies are outside the fences or the Governor's people. Besides the prison the thing I'm looking forward to the most is a certain sword-wielding badass. I just wonder how they are going to handle the things that happened to the character in that storyarc.