The global public relations powerhouses of Edelman and Ketchum are among the most powerful, effective, and engaging agencies on Facebook, according to the latest scorecard of social media effectiveness from Sociagility.

The London-based social media firm evaluated 25 of the world’s top PR networks for social media performance. When looking across the entire social media landscape — the Web, Facebook, Twitter, and YouTube — Edelman comes out on top for the second year in a row.

Break out the results for Facebook, and Ketchum tops the list. The rankings are a useful gauge of which agencies are not just performing for their clients on social media, but also for themselves.

Readers: What do you think of the results? Are you surprised by the rankings?