Oh for God's sake.
Maybe the project, or the role for that matter, wasn't up his alley. Perhaps this is just a simple case of an actor not being interested in the material enough to dedicate months of his life to it - especially now that said actor has really been hitting his stride as of late and has plenty of projects to pick and choose from.
Or maybe the script is a disaster. Who the hell knows. But by all means, let's jump to conclusions and assume the worst a year and a half out. I mean, Daniel Day-Lewis, Viggo Mortensen, and Chris Cooper all reportedly turned down roles for Batman Begins, and we sure called that dumpster fire of a film.
All sarcasm aside, it's Rick Flagg - probably one of the least flashy roles in a movie dedicated to several very flashy, scenery-chewing villains. I'm hardly going to get myself worked up because A-list actors aren't tripping over themselves and knocking down the gates at WB Studios to grab such a prestigious role.