The opinions expressed in this editorial are those of the author and do not necessarily reflect those of Decima Reports. What is a subscriber? Is it a mailbox, or a mobile phone account? A physical location, or an IP address? The recent spat between Vidéotron ltée and Star Choice Communications illustrates the difficulty of answering that question.  In its "account stacking" complaint to the CRTC, Quebecor Inc.’s Vidéotron cable distribution division argues that a subscriber is a single civic address. The Broadcasting Distribution Regulations certainly back up that assertion, indicating that a subscriber is a household of one or more persons to which service is provided by a licensed BDU. But is that definition still a valid one? It’s not the first time Quebecor has held BDUs to the coals over their definition of a subscriber. Backed by CHUM Ltd. and the Canadian Association of Broadcasters, the firm also weighed in on Look Communications’ proposed move from a wireless cable distributor to a mobile TV service provider. The trio pointed to the "household of one or more persons" language in the regulations, and maintained that the mobile devices Look would beam its programming to fell outside that definition. Ultimately, Québecor was unsuccessful in its attempt to deny Look a license, and the account stacking complaint has yet to be ruled on. But if the CRTC is to come to grips with regulating media in the digital age, the issue of what constitutes a subscriber is just one of many uncertainties it will have to resolve. The sooner the commission clarifies some of the language in the Broadcasting Act and its own regulations, the better.