Haven't seen anyone speak on this in this post.
Saw it last night.
Major problem with the ending.
Again, spoiler.
Amy tells FBI to check the tapes at Lake House.
When they do that though, won't they see she wasn't there for the last 30 days? Only 10 or so? That she arrived in a car with him without force? That she hadn't been locked up / held prisoner?
This was sort of touched on with Ben's comment on her escape and "How'd she get the box cutter?", but that was just skimmed over.
Any investigation by the FBI into her story would show she's lying. Also if Ben felt comfortable telling the female detective she's lying, why wouldn't he tell FBI?