I reckon twitter will merge with square and provide end-to-end advertising metrics for impressions --> clicks --> cart additions --> purchases. This will be valuable, and as much as I think twitter is silly, if they provide this they will do well.
Platform companies with stroes:
* Microsoft
* Google Play
* Apple
* [ empty ]
Super conflated and contrived appraisal here, but Twitter better post a strong offering in empty before facebook and they can't do that well without square and a platform or decentralized market. All this is to say, Twitter needs developers bad and to the extent they win them from Facebook and other platforms will be tied to the value they provide. I think that value will be provided by purchasing square in a merger of equals and building a dumb pipe platform, letting developers curate the content and providing stores.
We'll see what developer sentiment is, first few comments lead me to beleive it is not great.