Not really, contracting frees you from these chains. Even with an NDA the IP that MY company creates is the work of MY company, not the clients'. I respect the clients' side and need for anonymity and I make sure that what is mine stays mine and what is theirs stays theirs.
Just pick better companies. If you have the flexibility to choose contracting over employment, then you also have the flexibility to get out of market segments where these kinds of practices are commonplace. I have a friend that works for AT&T, when she describes her work environment, it really feels like a night and day difference from the Rails shops I work in and knock beers back with at meetups.
AT&T. Main thing there is the non-competes. Such a thing is unheard of in my world, but pretty standard amongst the myriad of companies that supply AT&T with chop-shop labor.