Mobile virtual network operator Virgin Mobile USA announced today it has surpassed the three million net subscriber mark, giving the company a 1.7% share of the U.S. wireless market.

Launched in July of 2002, Virgin Mobile USA has roughly doubled its subscriber base in the past year since reporting 1.4 million subscribers at the end of 2003. Many of the carrier’s customers come from the youth segment, which Virgin Mobile has specifically targeted via pay-as-you-go billing in addition to content from popular brands like MTV and Comedy Central.

According to Virgin Mobile, over 70% of its customers sent or received text messages in 2004, and over 60% used other non-voice data services. Perhaps most telling, over half of Virgin Mobile subscribers downloaded ringtones in 2004, amounting to about 8% of all U.S. ringtone sales in the last year.

Virgin Mobile USA is co-owned by Britain’s Virgin Group and Sprint, over whose wireless network the company operates. Rumors circulating in late 2004 suggested that Virgin Mobile USA was considering an initial public offering that could value the carrier at about $2 billion. A report in the Financial Times speculated the IPO would take place in the latter half of 2005, but at present, no further details have surfaced, nor has Virgin Mobile USA confirmed or denied such speculation.