Ask HN: How many of you willing to give gmail/yahoo info to expand the network

We are prototyping(just started) a social networking idea.

The question I have is: We want to have a sign-up page, where we will allow user to "create an username" and next step will be to enter thier gmail/yahoo username/pass(we wont store and we will say that) to fetch thier contacts so the user can know who is already using our service. The user if wishes can skip this step.

Initially, we were thinking of using openid and remove the "create username" step. But we thought not many people may remember thier openid. Another alternative was that they could sign in using thier yahoo/gmail account.

But the problem is it would be frusttrating for the user to once give us their gmail info to signup(i.e just creating the username) and then again to fetch the contacts(to see which of their contacts is using our service). Also many users may just want to checkout the services without expanding the network, so combining the above steps into one signon wouldn't also make sense, right? So we thought we should be going the usual "create username" route.

My questions are:

1. Do you think asking user to create a username would be a big hassle when compared to entering thier gmail id twice. What do you think?

2. My second question is more of what you would normally do. Normally will users give thier username/pass to a not-so-popular website? Lots of websites like stubleupon,linkedin,FB do this.

3.Also when checking out a new service, would you just want to create an username to check it out or also will you take the extra step to discover which of your friends are using? If they are not using, normally are you ok to send an invite. This sort of seems wierd, bcos you are just signing up, it would make sense for you to invite your friends without knowing if its good?