An interesting read in which Bruce Perens suggest several way to use proprietary software with GPL, the reason to do so? Lock-down or something that must be keep a secret, it could be considered to be more flexible, and also let GPL programs to be appliable in more places. He mostly talk about mobile devive, which still have lockdown like DRM or proprietary GSM stack.
http://itmanagement.earthweb.com/osrc/article.php/12068_3801396_2/Bruce-Perens-Combining-GPL-and-Proprietary-Software.htm -- :(){ :|:& };:
