You probably think mutual funds are the least likely activist investors. While that was true in the past, the tides appear to be changing. T. Rowe Price just did something it's only done once before in its 70-year history - filed as an activist investor in order to fight the management buyout of Laureate Education, according to the Wall Street Journal.

T. Rowe Price mutual fund manager, Brian Berghuis, ran the numbers and determined that the private deal valued at $3.8 billion for this operator of universities could be valued about 80% higher. Why did he care? T. Rowe Price mutual funds shareholders could be losing as much as $210 million according the the Journal.

Management buyouts tend to work differently than the more traditional outsider takeovers. Managers want to keep the price as low as possible in these deals, while they look for the highest price possible for an outsider takeover.

Fidelity Investments took a similar stance against a deal for a private-equity buyout of OSI Restaurant Partners earlier this year. OSI manages the Outback Steakhouse chain. Fidelity's stance worked and the offer had to be increased before shareholders would approve it.

It's about time that mutual funds take activist stands to protect their shareholders. Mutual fund assets totaled $11.496 trillion in August, according to the Investment Company Institute. As managers of their investors' money, mutual funds have an obligation to make sure people who hold mutual funds get the best bang for their buck. There's power in numbers and if the mutual fund companies became more active in protecting the rights of their shareholders, both stocks and mutual funds shareholders would benefit.

Lita Epstein is the author of more than 20 books including the "Pocket idiot's Guide to Investing in Mutual Funds."