One way to solve this is to look to Spotify. They changed their restriction: only playing music out of one device; into a feature: you can now control your music from any device. In addition to this, they used things like playlists, the discover weekly recommendations and other strategies in order to make it annoying to share an account. WHILE also having the barrier to getting your own account to the point where the annoyances (listening to ads, or paying $7.99 a month) are still better than pirating (possibility of low quality, no seeders, sketchy websites).

Of course this isn't to say this is how cable companies should exactly go about solving their problem, but by cracking down on their PAYING subscribers, they will drive more people NOT less to either pirate, or share passwords.