Twitter started the 'war' when they started limiting/blocking their API, of course it's 'their' data so they can do whatever they want with it, they just didn't do it in a decent way (or so some people think).
Twitter revoked access to the ability for Instagram users to find friends via its service, so maybe this is Instagram's payback.
The problem with these drives to cut off every developer for the sake of advert monetisation's that it's at the cost of user experience. For example, Instagram's web profiles felt rushed (they were basically useless for a few months). I don't wanna go to instagram.com everytime I wanna see a picture (which ends up being a stupid picture cos of all the filters).
Twitter's stealing ideas from third parties (the cashtag from stocktwits.com) and cutting off services with their own (pic.twitter.com, which takes forever to load images).
Soon we'll be back in the stone ages, redundant OAuth, no dev willing to use Android (and web) intents to share stuff ... [of course I am being silly by exaggerating]
