- Can you even Chromecast content that isn't from the internet? I have one and use it with Netflix all the time, but that's news to me.
- Typical living-room fare is only getting into XBMC or onto a hard drive/NAS if it's been BitTorrented. Streaming rules the day for me and for most people, it seems. (Not all of it is legal, of course, but people seem to vastly prefer illicit streaming sites to torrent trackers and clients.)
- OwnCloud is substantially more useful on a VPS so that you can access it from anywhere. Time Warner blocks incoming connections to its residential cable modems, last time I checked.
- IP cameras tend to be low resolution, low framerate, or both.
Of course local networks have their uses. What I contend is that very few people are actually constrained by the ~300Mbps of 802.11n.
Maybe the real application is business networking, so that remote desktop workstations could be practicable without wired networking.