I think that it's just easier to spend money on creating demand - Maroon's whole point about Google being the theoretical limit for targeting is that it's a hard task. Most people spend much more free time consuming media than discovering things, and it's the search part of discovery that is applicable for targeting.

Hmm, I wonder if you TiVo or the cable companies could mine your channel-surfing behavior to improve ad targeting (but that would require customized TV feeds instead of broadcast, yada, yada, yada). That would be interesting to identify other "discovery" activities that people do.

That said, I'd caution against using your imagination to assess ad spending. Ask the nearest small businessperson what they spend on yellow-pages listing.