but fb does have a search engine? Admittedly it only searches for content on their own site, but as you note the strategy has been to make the walled garden so

but fb does have a search engine? Admittedly it only searches for content on their own site, but as you note the strategy has been to make the walled garden so expansive that users would never want to leave (or be able to --- see India). Building a general purpose web search engine would be to give up on the "own everything" strategy.