I would make a judgement call but (a) I hate the idea of secrets, even "nice" ones that are surprises - if you don't want me to accidentally blurb it, don't tell me to start with, almost nothing good ever comes from not-nice secrets anyway, and (b) I especially dislike the idea of hiding things from my OH.
That said, I appreciate that real life sometimes involves people disclosing things, accidentally, or on purpose, that you'd rather not have known. If it affects me, my life, my OH, our DC, whatever, he gets told because he has a right to know. If it has literally no bearing on him (e.g. some dirty gossip about what A did to B and A/B are nothing to either of us), I fudge it under the rule of "stuff he wouldn't give a shit about anyway". Because he genuinely probably wouldn't. Otherwise if people ask to confide in me and I have a chance beforehand, as a rule, I make it clear that I don't keep secrets from my OH, so they should bear that in mind. Interestingly no one has ever stopped after receiving that warning, even though some of them didn't know my OH. As it happens he's the least gossipy person I know, so their secret wouldn't get out through him, but still. Some of them didn't know that.
Anyway, just my two pence.