mSpot is celebrating a milestone in the company’s history today. The mobile entertainment startup said it surpassed the 4 million subscriber mark – and it’s profitable, to boot.

The Palo Alto, Calif.-based company’s strategy has been to focus on on-deck deals with U.S. and Canadian carriers. Its services include access to music, custom ringtones, live radio and video on mobile devices. Among all its services, music is the most popular, said CEO Daren Tsui. “We’re big believers in music. We think music and mobile go hand in hand,” he said.

The company thus far hasn’t felt the impact of the macro economic doldrums, either, according to Tsui. mSpot has been growing steadily every year since its inception. Its first service – streaming radio –  was launched in April 2005. So in the near term, mSpot doesn’t need to go after another round of VC funding, he said.

To date, the majority of its products are white labeled, so end-users might now know they’re using mSpot. From the start, mSpot has relied on carriers to help market its services. “It’s a conscious trade-off we made when we first started,” he said. However, going forward, the company is at a stage where it can take a risk and plans to add off-deck to the mix.

Its Remix service is live on Alltel and AT&T, and it is in the process of adding other carriers. In total, mSpot powers 13 services across eight North American carriers.