Dan Thies PPC Permutation Video
Dan Thies of SEO Research Labs has an excellent presentation available on keyword permutations and the effect that this technique could/can/does have on paid advertising campaigns. Few advertisers actually use the permutation technique according to Thies, but it's certainly no secret. The basic concept is simple - you take a list of words and work up every possible combination of phrase and exact match bids. The result is a clear edge versus competitors (10-20% increase in traffic)who are running broad matches. It also offers advertisers valuable data on word order.