It’s not a two way system. Over the air digital is exactly the same as over the air analog in that respect: one way and one way only. Cable has always been somewhat two way if you have a box (which you usually need for premium channels, which is where the two way comes in) but is one way if you’re hooked straight into the TV. Satellite is similar to cable.
Not exactly. Satellite is "two-way" if the receiver is hooked to the phone line, thereby allowing the receiver to "phone home", telling the satellite company what pay-per-view and porno movies you've been buying.
DISH Network in particular always stresses to the customer to keep their receiver hooked to a standard phone line. That's utter bullcrap. You can actually get by without the phone line because if you ever decided to buy a pay-per-view movie you can do it online.
Both DirecTV and DISH Network have "customer portals" on their respective websites, which allows customers to order pay-per-view, pay their bills, upgrade and downgrade programming or get technical questions answered by other knowledgeable customers.
I've had DISH Network since 1998 and I don't have my recievers hooked to a phone line and I have had no problems whatsoever.