Mobile virtual network operators (MVNOs) have it tough. According to RCR Wireless News, Virgin Mobile USA's stock dropped more than 53% from its closing price yesterday after it reported a $14.7 million loss in the fourth quarter. The MVNO did, however, report net income of $4.2 million for the full year, making 2007 the carrier's first year to end in the black, the report said.

Here are some stats quoted from the article:

- The five-year-old company ended the year with nearly 5.1 million customers after adding 209,669 customers in the fourth quarter and 511,796 for the entire year.

- These numbers were down significantly from the subscriber growth it experienced in 2006 when the company added 613,752 customers in the fourth quarter that year and brought in 729,313 for the entire year.

- Churn increased incrementally from 4.8% to 4.9% for the year, yet dropped from 5.6% in the fourth quarter of 2006 to 5.1% in the last quarter of 2007.

The tech industry, and Wall Street for that matter, continue to wonder if MVNOs like Virgin Mobile and Helio will survive, given that Disney Mobile, Mobile ESPN, and Amp'd Mobile all failed in recent months.