This is notable because ringtones make up a great deal of 50’s earning power. The Forbes 100 deals with:

“… what kind of currency does the star’s name have,” she said. “It’s increasingly important how they are perceived both in industry circles and commercial circles, and this list represents who has cachet in both arenas.”

The AP article on 50 Cent’s inclusion:

Rapper 50 Cent never made the list before, but this year he captured eighth place thanks to his music, top-selling ringtones, and G-Unit clothing line. No other rapper made the list.

That’s really quite amazing that his ringtones rate a mention with his general music sales and a clothing line. It shows how much influence and power the ringtone industry is starting to have.