In this end of the year article, Prof. Strassler mentioned that hidden valley sectors could lead to some still open loopholes concerning the experimental discovery of supersymmetry and other BSM physics at the LHC such as certain kinds of extra dimensions for example. He only explains that these hidden valley sectors are some kind of an extension of minimal supersymmetric models and he does not explain this further when I ask him in the comments.
So I want to ask here:
What exactly are these hidden valley sectors, and how are they related to some kinds of minimal supersymmetric models, such as the MSSM for example? Are they rather ad hoc additions to the minimal models or are they embeded in some theories valid at higher energies?