Co-branded services may appear free but there is a hidden cost. Most of these sites would like your members, which you have acquired at great expense, to go directly to their site, not to yours. They want your members to remember them. You are competing for the attention of your stakeholders. Lastly, these services typically do not offer a complete range of community building applications.
Every community is unique.
It has a unique membership, unique purpose and unique needs. Open APIs allow customers to extend a standard, configurable product to support their community. CiviServer's open APIs enable applications that are community or member-centric to be built quickly. They also let applications be integrated into the Producers Workbench, thereby supporting customization and management by community producers. These APIs are the same ones that RealCommunities uses to build its range of applications.