Well, you're "morally obligated" to watch the advertisements. And, in a broadcast executive's mind, you're obligated to buy stuff being advertised, too, in order to prove that advertising is worth the money.
And no, you're not supposed to skip the ads, although I don't think that's really what's at stake here.
I think the real point has been mentioned elsewhere in the thread: allowing Aereo to do this without paying some license money to the broadcaster undercuts the negotiated licenses cable and satellite providers have to pay to the broadcasters to do essentially the same thing. If Aereo shut up and paid, they wouldn't be in trouble. But of course, they probably wouldn't be able to make money either. As stupid as it sounds, if a customer pays for a service that intervenes between the broadcast and the consumer, that service may be liable for fees to the broadcaster. I don't know about if the customer buys hardware (like an OTA Tivo to timeshift)... did they have to pay out license fees?