Topology Changes for SharePoint 2010 Logical Architecture
The "Shared Service Provider" is dead, it doesn’t exist in SharePoint 2010 and instead is replaced with new "Shared Service Applications". This allows core services to have their own security settings, run in their own applications and on their own databases.
There is even support for "cross farm" Service Applications (such as Search, User Profiles and the Managed Metadata Service) to allow distributed farm architecture like never before. Now in SharePoint 2010 you can scale up into multiple farm environments, allowing you to take advantage of more geo-distribution flexibility, and greater performance and availability from having dedicated farm hardware for important applications.
For the larger enterprise environments you have the benefit that different farms provide the opportunity to service different SLA requirements, and the Many – Many relationship for Web Applications to Shared Service Applications means that core enterprise level services can be shared globally, but smaller core specific services can be hosted multiple times, closer to the client environments, to service those farms that need them.
If you need greater security boundaries and better utilisation of resources you can spin up department specific farms for business critical organisational boundaries (such as HR and Finance) each with their own independent services or shared services (such as an HR specific BCS, or Finance and HR sharing their own set of Managed Metadata for payroll and accounting data, a service that is not provided to the more generalised collaboration and publishing environments).
All of this comes together with other administrative changes (such as the SQL failover awareness and Managed Accounts) to make SharePoint 2010 a truly industry leading platform for web applications and technology. I cannot think of any other product on the market that offers this level of flexibility across so many different technology streams.