I don't get the whole, "my phone number is secret" thing either.
I can understand not wanting to post it somewhere where it could get picked up by a marketing agency, becuase those calls are annoying. I just think that worrying about an individual abusing your phone number is borrowing trouble, since it more than likely won't happen. (And if that's not what the OP is worried about, then why does she care who has her phone number?)
If they call at an inconvenient time: don't answer.
If they call too often: answer only on your own schedule.
If you don't want to speak to a specific person: set their ring tone to silent, or just make use of your caller ID, and don't answer.
It's really easy to manage who you speak to and when, whilst still having the convenience of being contactable by those who you might need to liase with. It basically boils down to not picking up the phone if you don't wanna.
On the rare chance you start getting calls from a nutter, you can take more serious steps. But really, that's something that has a vanishingly low probability of occuring, and if it does, the solution is fairly simple (get a new number). I choose not to plan my life around low-risk, low-probability threats.