Mark Pincus at MobileBeat 2012

For the past few years, Sydney Finkelstein, a professor at Dartmouth College’s Tuck School of  Business and the author of Why Smart Executives Fail and Think Again: Why Good Leaders Make Bad Decisions, has ranked the worst chief executive officers.

This year’s list (which comes by way of Bloomberg’s Businessweek) prominently features social-game developer Zynga’s chief executive officer Mark Pincus at No. 4.

Finkelstein points to the company’s falling stock price, the exodus of top employees, and its overreliance on Facebook.

The responsibility for Zynga’s success and failures lies with Pincus. The stock price has fallen and a lot of executives have left the developer. But Finkelstein also claims that Pincus’s decision to “hitch his company’s wagon” to Facebook was a “rookie mistake,” and that just seems like something that is easy to say with the benefit of 20-20 hindsight.

We’ve contacted Zynga to provide Pincus the chance to comment, but the company has not responded at the time of this posting.

Zynga likely only achieved any level of success due to how intertwined it is with Facebook. Zynga generates nearly 80 percent of its revenue through the social network. Obviously, there was gold in those hills, and Pincus exploited the opportunity faster and more efficiently than anyone. Maybe his mistake was not creating a strategy for Zynga to disassociate from Facebook earlier, but Zynga does have a plan to diversify — and mobile games — even if it isn’t generating revenue like in the early days of FarmVille.

But diversifying, which everyone agrees Zynga must do, has caused some issues for the developer. In late November, Facebook amended an agreement with Zynga that ended an arrangement that previously gave the studio extra exposure on the social network.

“We have streamlined our terms with Zynga so that’s use of Facebook platform is governed by the same policies as the rest of the ecosystem,” a Facebook spokesperson revealed in a statement.

But that is just another problem that occurred on Pincus’s watch.