All this attacks are sure to come for project like bitcoin. I will say the most potent of all the attacks illustrated is the one from within and that is the one from both forks and the spamming attacks. Someone who is not techy savvy will not know how to spam the network to make things difficult neither will he be able to ensure there is a forked version of bitcoin. Its when all this inner fork are successful, before the one coming from external factors starting to take prominence such as the legal attack and every other attacks that want to come its way.