My colleague Tapio has asked in a post on his blog, what's best? To be public or private on Twitter?
To answer his question simply, I have tried both private and public profile settings on Twitter. I choose public because it's better at connecting you with other people. And that's the main reason I use Twitter. Good things tend to happen.
In comparison, choosing private settings creates a situation where fewer people gather online, but it does keep your online chatter private.
If you feel that what you say shouldn't be shared beyond your friends and family, lock the door. If you want new avenues to present themselves, open up.