Within an organization you don't need to worry about things like encryption and non-repudiation. While business process management is essential to B2B, the business processes that cross enterprises tend to be less complicated than business process management within an enterprise. Basically security is the big difference between the two. That's interesting, because recent reports state that most of the security risks are internal. While companies routinely do authentication and authorization, there tends to be less overall security on the inside.
Some companies have firewalls within the company.
So you're saying the difference between A2A and B2B is 10 percent or less. Yes, Basically the bulk of the integration problems are the same within enterprises and between enterprises. There are some significant marketplace implications. Integration vendors that spent most of their time in A2A, including Vitria, Neon, Mercator, BEA, and STCare all now touting themselves as B2B vendors. They just needed to add support for HTTP, XML, RosettaNet PIPs and similar process definitions, partner management and not a whole lot else.