It's often in IT that you see a case where an idea is brilliant in concept, but in execution the flaws become obvious. This is the reason most IT projects or code go through pilot testing to shake out the flaws. If caught early enough, the flaws can be corrected, or the requirements changed to something more practical. But at some point, the cost of changing what you have outweighs the benefits of change, so you have to just do your best and hope the product works out.
In The Men Who Stare At Goats, the main character and narrator, Bob Wilton, is a reporter who travels to Iraq to find some worth in his life. There he meets a man who claims to be part of a secret army crew who are referred to as "Jedi". Throughout the film, Bob plays the neophyte follower who is trying to learn about their "Jedi" ways. As such, he often asks plenty of questions about the "Jedi" and acts confused when new concepts of the "Jedi" are discussed.
In a brilliantly clever, but ultimately undoing casting decision, Bob is played by Ewan McGregor. Anyone who has seen the recent Star Wars films can see the ironic humor of Obi-Wan Kenobi going around befuddled by these New Age "Jedis". If this had been a throw-away concept, a one-time joke, it would have served the film as a clever aside. But, with Ewan / Obi-wan glaring back at you as the narrator constantly confused by references to Jedi, I found it impossible to relax into the film. Instead, it became a meta-character. When the character is not so much enhanced as dependent on the actor being recognizable in another role, and that joke is hammered home repeatedly, the result is you have reminders that these are actors.
Yes, I realize that I was sitting in a theater, and I paid money to watch a film, and yes, these films have actors, and no, it's not real. My problem come in with suspension of disbelief -- the ability of the audience to accept the concept of the film in order to enjoy it. For instance, it's very difficult to enjoy Star Wars if every time you see the Millenium Falcon jump to hyperspace, you snort and deride that is ridiculous. An instance more similar to the casting problem is breaking the fourth wall, where one of the characters address the audience directly. This does not break suspension of disbelief BECAUSE the characters stay in character. It would never work for Woody Allen in Annie Hall to say "You heard that! I know because I wrote this script!" versus "You heard that!" Ewan McGregor as Bob doesn't break the fourth wall, it sneaks around it. It's funny as a Saturday Night Live skit, but not as film.
If the character of Bob is played by ANY other actor (except Liam Neeson or Mark Hamill -- the latter being the most distracting), then entire feel of the film changes. Instead, I have to wonder if the script was written precisely with Ewan in mind, if the producers where intending you to go, "that is ironic and funny that Ewan is asking about Jedi again" every time he's up there, or if there was a pilot process to any of this.
And then there's the ending. The very last scene changes the entire feel of the preceeding 110 minutes. I'm not going to spoil it for you, but I'll guess that you, like me, expected an entirely different result to Ewan's experiment. Where most of the film is grounded in psychic powers that may-or-may-not exist, but if they do they certainly aren't capable of some things, then the end is completely head-shaking.
Did I mention I liked the film? It's a solid 'B' experience, except for those two things. Casting and end. Come to think of it, that's grounds for an official "bungling in execution" label. Next time get Harrison Ford. Wait, maybe not...