This title makes no sense to me at all.
So Runner Runner is the story of a college boy who ends up gambling all his money to try and fund his college tuition but loses it to some online gambling cheats. He goes to the manager of the online gambling site to tell him someone is cheating on his website and the boss is so impressed with him, he asks the guy to join him. And the story goes from there. Add in shady-boss manipulations, a romantic love interest and you have Runner Runner.
At it's core, Runner Runner is a pretty formulaic gambling movie. It's got the underhanded boss, the pretty love interest and the do-gooder protagonist. Sadly, it never really rises above the formula as most of the characters remain flat and uninteresting. Justin Timberlake? He's a guy caught in a hard situation who ends up being used. That's his thing in the movie and he never goes beyond that. Gemma Arterton is the hot love interest and that's pretty much it for her.
However, I'm going to have to give credit to Ben Affleck for his portrayal in the movie. Despite never rising above the characterization of scumbag boss, he manages to do it very very well and may very well have been the best actor in the movie.
Overall, I'd say Runner Runner is a passable use of time but is strictly a 'watch once' kind of film. And also, Gemma Arterton is hot.