Why?
Everything successful fb has done in more than a decade is copying or acquiring competitors.
Zuck has spent a few years setting $36,000,000,000 on fire building secondlife2, that nobody wants. The stock is down 25% in the last 2 years.
facebook is like google, both are advertising companies at their core. They both leveraged one idea to serve adds really well and have failed to produce anything new in house since.