Well, if this sort of agreement becomes widespread, it would effectively opt them in to being sued by other companies who have patents assigned under a similar

Well, if this sort of agreement becomes widespread, it would effectively opt them in to being sued by other companies who have patents assigned under a similar contract. Also, it would be in breach of any other IPA contracts they've made with other inventors. It's a neat concept. The more widespread these contracts become, the more litigation you expose yourself to for using your patents offensively.