In theory, since DVR users typically don't see a commercial, they may not be enticed to purchase a product based on seeing it or learning about it from a commercial. Eventually, advertisers will not see the benefit of paying for commercial time.
Currently, the networks are NOT hurt. I was part of a "test" with Nielsen of DVR users and though they asked if we recorded a show and watched it later (they don't care so much *when* you watch vs did you watch), they didn't ask if we skipped commercials. Do they assume ALL DVR users do ? Anyway, this is how networks come up with their per-minute charge for commercials, that is, based on the number of viewers of their show (not the commercials !).
As far as double-dipping, well, they've been doing it so long now that it's normal for them, so to take half of their income away, yeah, they will fight that !
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