There have so much money and software-based anything generates so much revenue with a relevant investment that this apparent nonsense seems self-sustaining! This project, for example, is likely to not lose a dime, even to generate profits, independently upon its final outputs. After injecting a relevant amount of money, Facebook might start applying for R&D grants/prizes which will most likely earn; just this might be enough to account for all the costs during some years. Additionally, it will be very positive for the public image of Facebook as a game-changer and R&D-focused company. All the workers and managers will get lots of money, excellent experience for their CVs and lots of relevant knowledge (even in case of not reaching a proper product, working on so demanding projects is the best to get top-level expertise). Facebook might even get some further direct benefits via commercialising preliminary versions or merchandising.
When you have enough money to invest, losing in software is virtually impossible, mainly in a place like Silicon Valley which has already an important intrinsic value (virtually anything from there gets lots of attention/free advertisement and is appealing to customers everywhere). I mean having more expenses than earnings, because in case of bringing costs of opportunity into picture too, all these jokish projects would be pure losses. But I guess that nobody cares/knows as far as the apparent profit continue flowing.
Someone might think that people like me might be unhappy with such an unfair situation, but I do fully accept it. Note that my personal situation (as the one of most of programmers/software-companies outside a few privileged areas) is completely different than all that: no investors, no opportunities, no money flowing around, having to do everything perfectly to be systematically ignored, not having any kind of support (for most of people in the town where I am now programming isn’t even an actual occupation or cannot understand what remote work is), etc. Although I would certainly love working under better conditions, I wouldn't ever renounce to some of my current benefits (e.g., doing what I consider right without tolerating ignorant arbitrary impositions); I am also sure that most of people working on these generating-money-from-nowhere projects are systematically tolerating what I would never do. That's why I don't envy those programmers and think that this Silicon Valley apparent nonsense is likely to continue existing for a while (and, hopefully, the TV series forever! Season 4 premiere on Sunday!!).