Here’s some useful advice from Chris Dixon for companies that are trying to build products without getting run over by platform vendors:

Normally, when third parties try to predict whether their products will be subsumed by a platform, the question boils down to whether their products will be strategic to the platform. When the platform has an established business model, this analysis is fairly straightforward (for example, here is my strategic analysis of Google’s platform). If you make games for the iPhone, you are pretty certain Apple will take their 30% cut and leave you alone. Similarly, if you are a content website relying on SEO and Google Adsense you can be pretty confident Google will leave you alone. Until Twitter has a successful business model, they can’t have a consistent strategy and third parties should expect erratic behavior and even complete and sudden shifts in strategy.