Animation Age Ghetto killed it.
I saw this movie the week after it came out with a friend and we both loved it - in fact, I loved it a lot more than I thought I would since I'm not a Pooh fan by any means at all. I'm disappointed that word-of-mouth never really caught on with this movie but I think I know a very obvious reason besides opening the same day as a little movie called Harry Potter: the Animation Age Ghetto.
When I told my parents that my friend and I were considering likely seeing Winnie the Pooh that day, my mom freaked out at the proposition. She tried doing everything while I was home to try and stop me from seeing it, suggesting other movies we could go see, etc. And she supposedly kept dwelling on it after I left the house to meet up with my friend. I lied to her that night and said we say Zookeeper instead. Bear in mind, this is the same woman who had a huge problem with me seeing The Princess and the Frog in theaters.
I hate to make assumptions, but for many teens I'm sure this similar situation happened to them when they tried to see this movie. They had to listen to their parents bitch and moan so much that they decided to stay away. And adults just said to themselves "Silly Disney, 2D animation is for kids!"
Look, I know this is technically a movie for little kids but it was a great film for all ages on top of that. I think Animation Age Ghetto was a big reason it didn't do as well as it should have.