* To operate in multiple countries so people can stay connected you have to abide by local laws even if they don't match the typical values.
* Social media is inherently winner-takes all due to the requirement of critical mass and connectedness. The winners have shifted over time (myspace) before but it seems harder to do than with other consumer services.
* Moderation of billions is a hard unsolved problem and is a game you can't win. You walk the tight rope of either allowing hate speech or being too overreaching in censoring. I'm not sure other startups will solve this any better.
* I'm personally not a huge fan of governments messing with competition, especially not for services where the people themselves choose to use it or not. Some share of people like using facebook and I don't feel banning them for the sake of their success is the right solution. While I'm from europe myself I feel over-regulating is one (among many) of the reasons why there are almost no dominant tech players here.
* Monetisation and use of user data. While there are other monetisation paths many people are actually ok with the trade of their data for features and should have this choice. The larger tech companies probably have some of the most well organised and privacy aware advertising platforms compared to smaller players where the likelihood of privacy incidents is arguably higher.