Obviously you need enough coax for what you need to do today, or could reasonably see yourself doing in the future - so you need one now, but maybe want two if there's even the slightest chance you might want to add an AM21 for OTA capability, or might become one of the crazy people who pay for both Directv and cable TV. But four? I have a hard time seeing any possible future where you'd ever need that. Yeah, its cheap to pull, but a lot of people seem to go crazy with pulling coax that they never use, kind of like all the "smart" people a decade ago who thought they were being smart pulling fiber in new construction which isn't and will never be used in a home environment by consumer products.
You're much better off pulling extra cat5/cat6 than pulling extra coax. There will never be any new technologies that use coax, but at some point everything that uses wired cabling aside from 120v/240v AC is likely to converge on cat5e/cat6a. For instance, the new HDbaseT spec will see TVs soon available for sale that include RJ45 connectors for HDMI input. There is more and more (typically commercial so far) audio equipment that uses cat5 for balanced line level audio. It is often used in low voltage applications for carrying IR and various sensor inputs for burglar alarms, water alarms etc. Security cameras often uses cat5 these days, even when it is a simple composite video signal (if for no other reason it makes it easier to upgrade to IP cameras in the future, which of course use cat5 and are often powered via the same cat5 cable)
At some point in the future I think we'll start seeing cat5/cat6 replacing coax for cable and satellite TV. Instead of sticking five tuners in a Genie, stick 8 or 16 tuners on a single chip in a SWM multiswitch or SWM LNB and have it output a single cat5 cable carrying the tuned channels via IP that DVRs, receivers or RVU devices can select. There's a lot of coax already out there so it won't be something they'll retrofit, but I could easily see it becoming the preferred method for new installs within the decade.
SL5, 2xSWM16, 16 H20-100, 1 H20-600, 7 H24-700/AM21, 2 H10-200