Not on steem. AFAIK you need 20 witnesses to run a steem block chain. So we would need to become witnesses first before we can fork the chain.

Of course you could set up 20 sock puppet witnesses but who would want to use that chain? And it's still be witnesses.

Same for any other blockchain. You always need a sizeable group to add validity to your fork.

So not anyone can fork a coin. It takes a sizeable group to fork a coin.

At least 20 in the case of steem.