The picture if the Headhunting market is a little outdated but the conceptual map and the trends for the future are interesting.
From a practical point of view, double checking names and existing players seems to be a basic piece of advice to anyone, company or individual, seeking new positions.
Well written and documented, it also provides the history of headhunting/recruiting as a business, mostly spun off from the early accountancy firms in the US (15-20 years later in Europe).