Donald Yacktman is known for taking investment gambles with his $19 billion mutual fund. The firm is unique for its support in a number of undervalued stocks, and now the company may be taking its biggest risk yet. Yacktman Asset Management doubled its stake in Research In Motion (RIMM) last quarter by purchasing an additional 12.2 million shares in the company. Despite a falling market share, Yactman, like a few others, is confident in the 80 million worldwide BlackBerry users and the upcoming BlackBerry 10 operating system.

“People do like to use the keyboard, and there is a big embedded base,” Yacktman said in an interview with Bloomberg. “This company could be worth a lot more.”

While the struggling vendor’s stock is still down over 30% from last year, in the most recent rally shares of RIM have climbed 70% from their late September low. The company’s stock recently saw impressive gains for eight straight days before dropping 11% on Tuesday, the biggest one-day drop since June, following a report from Kantar Worldpanel.

The recent purchase has increased Yacktman’s stake in RIM to 4.5%, making it the firm’s fifth-largest shareholder.

Analysts continue to fight over RIM’s relevance. While some claim the company’s loyal user base will make BlackBerry 10 a success, others cite Palm’s failed webOS platform and the increased competition from Android and iOS as reasons to fret.