We finally dropped our landline phone service after we discovered our line had been dead for a week without our even noticing. The lack of telemarketers was nice! If anything, cell phones are more reliable- cell towers at least have generators. And redundancy. And if recent uproar over the nanny state is any indication, can pinpoint your location as well as a billing address!
As for a UPS on the cable modem... works fine when the problem is a downed line or blown transformer in the neighborhood. 9 times out of 10, though, if our power is out in the house- so is the cable company's equipment. If you shut your PC down fast enough, a 700kVA UPS will leave a cable modem and wifi router up longer than a laptop can run on battery
