Vast majority of DRM schemes are broken, and I think it says something about security through obscurity....
Yet, though VideoGuard salletite/cable TV drm scheme remain unbroken for 8 years, despite the fact that is very popular and really sucks (you need their set-top-box to view it)
and its really frightening that one day they will create a scheme that can't be broken....

They won't even warn you, but will just charge 125$ per every excess GB.
This poor blogger was asked to pay 1200$ by this devil company.