I don't like the "patent troll" business model, but, if I buy a business then I expect to monetize its assets. THAT is exactly what is happening with patent holding companies. There is nothing new in that concept.
What I really don't like is asserting patents of dubious value (if any) in the hopes of extorting a license vs the cost of a trial. This is what I believe VirnetX is doing. The number of patent suits arising from patent holding companies, that are then deemed invalid is quite large, and it appears this will happen with VirnetX's suits against Apple.
Patents are entitled to a legal presumption of validity until a court says otherwise (or the PTAB if there is no appeal). So it is what it is.