But isn't Twitter's unwillingness to ban unless in instances of overwhelming PR part of the problem? (i.e. the harassment issue that has legitimately driven away users)
It may be the case that it is simply impossible to serve too large a diversity of users out of one central service. Even ignoring the proximal political issues that people are thinking of right this second that are centered in the US, there's a lot of cultures in the world, with a lot of social norms in active conflict with each other, and a lot of nations who have various interests in enforcing those social norms and whose interests appear to be growing rather than shrinking. For a similar example, it is increasingly difficult if not impossible to run an international backup service housed entirely in any one country... you must have the data housed in an acceptable jurisdiction for your customers and there is no one jurisdiction acceptable to everybody. It may the case that Twitter's current issues are not an anomaly, but a fundamental aspect of trying to run an impossibly large service. Going back to those "proximal political issues", they may not be an anomaly... they may simply be a specific instance of an inescapable general problem.
Facebook is facing similar pressures. Their valuation still seems to assume they've got a lot of growth potential, but what if this circle can't be squared? It isn't hard to imagine the possibility that not only has Facebook more-or-less grown as much as it can, give or take some stragglers, but that it may even have grown more than it can sustain, in which case it is grossly overvalued.
Facebook is facing similar pressures. Their valuation still seems to assume they've got a lot of growth potential, but what if this circle can't be squared? It isn't hard to imagine the possibility that not only has Facebook more-or-less grown as much as it can, give or take some stragglers, but that it may even have grown more than it can sustain, in which case it is grossly overvalued.