But when I go to a website I expect to get the content. I don't expect the owner to use my computer for mining. That seems like unauthorized use to me.
While I don't think that's actually how the law can be interpreted, it does get at the central issue most computer users/researchers have with the law. It allows different standards for what "unauthorized" means, hence it is very elastic and can easily be abused, especially when combined with the plea bargain process (@see Aaron Schwartz).
But when I go to website I expect to get the content. I don't expect the owner to use my computer for running a bunch of tracking ad code. That seems like unauthorized use to me.