Most of these companies are multibillion-dollar corporate entities, traded as public corporations on the stock exchange. The majority of these companies are owned by investment institutions. All have traditional corporate structures, with a president, and a board of directors.
Analysis: These companies have found a strong overall structure, which will greatly help them stay the large and powerful corporations that they are. However, their size does present a challenge to them, as they have to consistently find ways of cutting costs. Comcast, for example, is the largest company, but has a reputation for poor customer service and satisfaction. Additionally, the size of these corporations makes it less likely for truly innovative change to come from within - usually, it comes from entrepreneurial competitors, such as Netflix. While this does not mean that the structure of these companies, or their sizes, is necessarily a bad thing, it is not solely a positive either. It requires a great deal of work on the part of the company to make it work, otherwise, the company will slowly wither away under better competitors.
Sources: http://www.annualreports.com/HostedData/AnnualReports/PDFArchive/twc2010.pdf
http://www.sec.gov/Archives/edgar/data/1166691/000119312511047243/d10k.htm#tx100440_1
http://www.theacsi.org/index.php?option=com_content&task=view&id=86&Itemid=90