Based on what he said at the time, he felt that it was too difficult to evolve #'s component specs (mostly designed & controlled by Google) once Google decided that # and interoperability in the social space was no longer desirable (coincides with the launch of #). On top of that, his company was losing money (at one point, it was ad-supported, but users rebelled against the most lucrative ad provider, Google), and most SN users relied upon him for zero-price hosting.