Good point Mike.
How would you prefer to share your information? Do you need more clarity as for what will be available on your user profile to others and what stays confidential?
I guess it would help to know what stays on my PC, what is shown to others I invite, and what goes to your server for the invitations. The issue is where is the data held and when is it viewed. In addition, why is it needed. Why do you need my birth date?
I think answering these questions will make it more comfortable to know what to answer and what not to answer. Make non-relevant information (birth date for example) non-required. They need to be answer on the form where the information is entered. For some people this may still be an issue. But I'd feel better knowing the above.
Thanks.
Mike