I don't worry about passwords, as none of mine are remotely connected to me, and a 'hacker' would need to know my bank details in order to use them anyway.
I am careful about what I post that refers to my personal life, and have asked people I trust on here to let me know if I do post anything identifying. I don't think people could work out who I am from my posts. For one thing, I am not in the public eye at all, so there is nothing to go by, and for another I'm not interesting enough for anyone to bother. I do think that if someone I know read one thing and thought 'Oh, Ddog has one of those, or goes to Timbuktu for her holidays' they could connect other posts and confirm their suspicions. I would hope that a true friend would respect my privacy and not do that, but people can be nosy.
Does it matter? Not really, but my concern would be that something I say on here might be taken out of context and reported to someone I care about. I am honest about my opinions on here, but like most people I am more careful about expressing them 'in real life' where I don't really discuss politics, religion or money with acquaintances.