Kevin Marks, who was behind many of Google’s social initiatives, has left the company—the latest in a long list of well-known employees to depart recently. At Google (NSDQ: GOOG) Marks was involved in almost all of the company’s social efforts, including Google Profiles, social networking site orkut, as well as its OpenSocial initiative, which makes it easy for developers to create apps that can run on multiple social networking sites. On his blog, Marks doesn’t explain why he is departing although he says that he will be “working on web standards” through a variety of groups and “coding, writing and speaking on the social web via several new projects.” (He tells TechCrunch that “Over the last two years, we have built out the infrastructure for the social Web. Now it is time to build things on that infrastructure” and adds that he is ready for a “small company phase”). Google has started several efforts—including the creation of an algorithm—to try to improve employee retention.