This is a good point and relates to what Stevenj said "As long as Mark Zuckerberg is CEO". I would add to that "and as long as he, and his collective team maintain the vision". Yahoo, over the years suffered from both of these missteps. Apple did to, and then the vision came back. We all know how that turned out.

What was/is Yahoo!?

Was it a search engine? Was it a portal?

Is it a news site? Is it a media site? Is it a portal? Is it a tech company?

I think Facebook will always be a social network that's focused on building its core product(s) with good technical people.