As previously mentioned, commercial minute ratings also hold the networks accountable for prior malfeasance in formatting commercials, particularly outside of network primetime.
Some late night programs had been jamming ads into the lower-rated last half of the show. Late Show with David Letterman (CBS) was a particular offender and the program was reformatted to move commercials to an earlier, advertiser-friendlier position. Jimmy Kimmel Live (ABC) used to contain a non-program break that was eight to nine minutes long (also in the back half of the show) – that’s now gone. Similar transgressions in the early morning daypart are now under scrutiny. Some cable networks with notoriously long commercial pods (i.e. MTV, VH1) have changed to shorter breaks (albeit more breaks per hour).
Additional benefits may be forthcoming. Cable networks that dilute commercial audiences by airing promotional announcements in "A" positions or running national ads after a show ends will not just hear media buyers whine about it, they’ll face the wrath of the god Nielsen, and subsequently their CFOs.