Facebook has been absorbing high-level staff from rivals in the past 12 months, including Google's Sheryl Sandberg, Elliot Schrage, Benjamin Ling and Justin Rosenstein, and YouTube's Gideon Yu.
The aggressive acquisition of experienced people heads off criticism from analysts that the social networking phenomenon does not have the management wherewithal to cash in on its popularity.
Schroepfer has overseen the development of Firefox versions 1.5, 2 and 3. Previously he was chief technology officer at Sun's data centre automation division, arriving at Sun when the company acquired CenterRun, a company which he founded.
Facebook has recently overhauled its user interface emphasising the spontaneous social news aspects of the site, a move widely seen as a reply to competition from micro-blogging sites like Twitter.