In addition to these theories, I would also guess that developers have realized that Twitter could simply replicate their feature sets and make their client/service the default choice. This is of course, Twitter’s prerogative, and is also the risk developers undertake when building for a platform they don’t control.
I have no doubt that Twitter wants an ecosystem to thrive around its platform, much in the same way that Facebook wants an ecosystem around its social network. However, as I wrote all the way back in July of 2008, VCs must wise up to the fact that investing in accessories that can be reproduced and easily packaged as part of a core offering may not be the best business strategy.
link: Venture capitalists tire of Twitter-y start-ups – CNET
