Short sellers trading stocks listed on Nasdaq made big bets against cable and financial shares, according to data from January 15. The numbers compare to short interest in the same companies on December 15, 2007.

The short interest in cable company Charter Communications (NASDAQ: CHTR) moved up 4 million to 99.3 million. Charter's stock has fallen close to $1. It carries $19 billion in debt and there is a growing concern that operating profits will not cover interest. Controlling shareholder Paul Allen may have to put more debt into the company.

Short interest in Comcast (NASDAQ: CMCSA) rose almost 600,000 shares to 45.1 million. After hitting a record high last year, shares of the nation's largest cable company have fallen one-third on concerns that large telephone companies will take its TV and broadband subscribers with their new fiber-to-the-home products.

Short interest in E*Trade (NASDAQ: ETFC) moved up 9.9 million shares to 91.2 million. The market is obviously willing to bet that there are more problems with the company's balance sheet. Short interest in healthier rival TD Ameritrade (NASDAQ: AMTD) fell 5.1 million to 8.6 million shares. The market is not shorting the discount brokerage industry, just the weakest company in the group.

Douglas A. McIntyre is an editor at 247wallst.com.