My experience with DirectTV and the phone line is that they only require a phone connection if you have more than one receiver at your address, and are paying for that extra receiver with only $4.99/month. They want to be able to address each receiver and/or instruct each receiver to "phone home" randomly to ensure that you actually do have all of those receivers at the billing location (through caller-id, perhaps?).
That was what they told me, that if I couldn't connect both of my receivers to a phone line that they'd have to charge me fully for two separate and independent receivers rather than allowing all my programming on the second receiver for just $4.99. Interestingly, I just added a third receiver last week and they didn't insist that I connect it to a phone line. They simply told me I'd be paying yet another $4.99 for that third box. Maybe they don't care any more about confirming its location, or maybe they just assumed I connected it to a phone line as expected. Maybe I'll find out in a few months.
And of course you would need a phone connection even with only a single receiver if you want to utilize pay-per-view services.
Incidentally, I didn't have phone jack near my primary two receivers, so I bought a set of wireless base/satellite stations (from RCA, I think) at Good Guys. They work perfectly, through the A/C power in my home.
