From the press release on yahoo:
Sounds like they also have some analytic systems ogletree. Having an in house analytics system that can be more easily customized and automated is a big plus.
Really only a handful of things (in my mind) you could valuate an SEO/ Internet marketing company on.
-Human resources/ intellectual property (good people)
-Quality of Analytics/ Automation of systems
-"Network" reach (content, ad inventory)
-Vision (good management)
It looks to me like they are very strong in all these areas in comparison with the other large firms. The future of SEO is simple (much more than we'd like it to be probably): content and links. They realized this quite a while ago, and have been hoarding both as much as possible.