Thanks guys, those explanations make sense. My house does have a satellite dish on it (never used it), and the way the wiring all meets looks like it could be for what you describe. It all comes together in one Bell Atlantic box that I don't fully understand, but I do know that it has a coax splitter in the middle of it that does most of the work. Of course, I only have one line in use, making the other 9 unnecessary.

I guess I'm surprised that this brand new house would need two coax to every location. It's also in an area where not a lot of people probably have dishes due to very tall, old trees, and I'm pretty sure Fios is there too. I'll have to figure out how to wire up 13 pairs! I'll probably start with a 2-way splitter - one to the router and one to a 4 or 8-way splitter that will handle the locations they know they'll have TVs on (size of the splitter will depend on how many drops they need live, of course).

Should be interesting!