I think everyone has secrets. Maybe not babies, I don't know. Never asked them.
And I think everyone's pretty good at keeping them, when they really want to.
As such, I have a bit of a theory: people only really have a few secrets that they'll actually put in a fair bit of effort into covering up and such. Most other things that people don't know about will be more along the lines of, "Don't ask, don't tell."
As an example, I've only got two real secrets. No, I'm not going to tell you what they are. This is why they are called "secrets". I tend to go by the old maxim that the best secrets are those known only to one person, even if it is a bit incorrect. I reckon a dead person would be even better at keeping a secret, and no persons even more so. But that's just what I think.
Both of those, however, I'd be willing to share with a few people at the right time. I don't think it's good to keep secrets from everybody. Some people have that as their job, unfortunately. I'm very glad that isn't me.