The problem I think I'd encounter with a blacklist is that skirting it suddenly becomes an interesting challenge. Proxies and VPNs can get me where I want to go, and the idea that I'm not supposed to makes it more tempting. If I implement a whitelist and block my work comp's MAC address from accessing the admin panel on my router, then I'd have to physically get off my ass in order to circumvent it, in which case It'd be easier to just do the damned work.