jautor's spot on. Not running RG-6 is weird. Normal is one per room, basically every house in the US has that, and no more. Security cameras are going CAT-5, and even if you install wiring for one now, and use one that uses RG-59, it's baseband, so you can use baluns. The current generation uses CAT-5 directly without Ethernet or IP ability, and the next generation after that will be IP.
I would say that while the HD transition and dual-tuner satellite DVRs are behind us, DirecTV's current coax system (may be the same for DISH, not sure) cannot be multiplexed, so if you want OTA and DirecTV, you'd need two RG-6s. If you're using any ONE MSO, and nothing else, one RG-6 is 100% good to go.