Since those SEC filings can be filled with such dry legalese, I figured I'd save you the trouble and highlight some of the most interesting parts.
Note for the particularly crazy: Italics portions below were added by me.
[O]ur ratings are the primary metrics used to determine the value of programming and advertising in the U.S. total television advertising marketplace, which was approximately $77 billion in 2008[...]. Balancing the needs of our paying clients, while managing to consistently under report the ratings of shows favored by certain fans without discovery is an ongoing risk of the business.
Our business uses scanners and diaries to gather consumer data from sample households as well as Set Meters, People Meters, Active/Passive Meters and diaries to gather television audience measurement data from sample households. It is increasingly difficult and costly to obtain consent from households to participate in the surveys. In addition, it is increasingly difficult and costly to ensure that the selected sample of households mirrors the behaviors and characteristics of the entire population and covers all of the demographic segments requested by our clients. Additionally, as consumers adopt modes of telecommunication other than traditional telephone service, such as mobile, cable and internet calling, it may become more difficult for our services to reach and recruit participants for consumer purchasing and audience measurement services. If we are unsuccessful in our efforts to recruit appropriate participants and maintain adequate participation levels, our clients may lose confidence in our ratings services and we could lose the support of the relevant industry groups. If this were to happen, our consumer purchasing and audience measurement services may be materially and adversely affected. In addition, public scrutiny of our methods has made it increasingly difficult to fool all the people, all of the time. In the future, fooling some of the people all of the time, or all of the people some of the time may be the only sustainable business model.
Due to the high-profile nature of our services in the media, internet and entertainment information industries, we could become the target of criticism by various industry groups and market segments. We strive to be fair, transparent and impartial in the production of audience measurement services, and the quality of our U.S. ratings services are voluntarily reviewed and accredited by the Media Rating Council, a voluntary trade organization, whose members include many of our key client constituencies. However, criticism of our business by special interests, and by clients with competing and often conflicting demands on our measurement service, could result in government regulation. Fans of many canceled television shows are unable to reconcile their level of interest with the reality of the audience measured for the show, causing increased burden on the national mental health infrastructure which could increase the calls for government regulation.
Note for the particularly crazy: Italics portions above added by me, the rest is from the SEC filing.