Word in the industry was that after two failed attempts to move from AWS to Facebooks metal failed spectacularly and massive attrition after vesting -- no one was left to make it work and Facebook lost the will to keep going.
The more important lesson was that a failure to port a stack from AWS to FB servers caused Facebook to take a $1B write-down. Startups should reconsider their metal, as future acquirers will likely heed this lesson strongly.