Great post on Max Levchin’s blog on how to engineer the social conditions that make people want to build on and into your platform.
Some observations from his list:

• Visiting and engaging the CTOs of pre-launch partner companies will create instant camaraderie between the platform development team and the developer community.
• Treat developers equally, but leverage the best ones by letting them closer in. Plan and manage a community, and introduce a community manager early – ideally, these are pretty technical people that gain fast credibility with hard-core developers. Introduce a few colorful personalities to make developers feel welcome, pre-launch.
• Shift the support/documentation load onto the early developers.
• Respond very quickly to platform issues, and take the early scaling problems seriously. The feeling of “this must be really important to them” will carry a lot of weight with the developer community in the early days.
• Emphasize the money-making nature of the platform.

There’s lots more, all shrewd and all true. Talk about getting a fence painted.