Pay-Per-Click (or Google Adwords) as related to Television Advertising (or any broadcast marketing):
Ad Campaign = Group of ads for one specific Product or Service
Ad Group = The Actual Television Commercial
Keywords = TV Channels or Radio Stations
what do you think?
Also, PPC advertising doesn't have an equivalent of Nielsen or Arbitron ratings (independent auditing services). The "audience" size is determined by Google (or Overture or whoever) with the possibility for confirmation by the advertiser with log analysis.
I'd assume having a 1% conversion rate on a TV commercial would be phenomenal whereas 1% on most my PPC campaigns is far below the acceptable level.