Another issue for public blockchains is the existence of network forks. Bitcoin has been forked twice, splitting into Bitcoin and Bitcoin cash, then again into Bitcoin Gold. There are now three independent networks claiming the Bitcoin mantle. While the original network is still by far the most dominant, all the forks were a result of a breakdown in agreement among the key network participants about the future of the technology.
Ethereum suffered a similar fate, splitting into Ethereum, and Ethereum Classic over how to respond to the DAO hack. The majority felt that the DAO should have the hacked funds restored, but a strong minority disagreed, asking why should this hack get special treatment over others?. The result was two networks, one with the hacked funds restored (Ethereum) and one where the network protocol was the rule no matter what (Ethereum Classic).