Question about Facebook Connect

I don't have it on my site, but I just tried it on the demo site. My question is, is there a way that once they join via facebook, they can change their username only once, then not be able to change it again? I have my site so members cannot change their username, because if their profile is www.mydomain.com/user, and they change it to www.mydomain.com/newusername, Google will start penalizing for pages that no longer exist. I like the facebook connect feature, but first names won't work with the Niche I'm targeting.

And also, it uses your first name From facebook for your Dolphin username, what happens when you start getting people with the same first name? I probably have 30 guys on my site with the first name John.

Yes, using any form of sign up you can edit your profile to any username that is available, once a member joins, they can edit their profile to the username they prefer. If you want you can set to reconfirm user info if they do change their name.

You really don't have the option to stop the name change.

Please show evidence of this claim..

Google will start penalizing for pages that no longer exist

I think you may be incorrect on that.

Google may penalize you if you have links to pages that no longer exist. This applies to your own site. For example a link in your navigation that links to a page that does not actually exist.

However, this would be rare for user name. You do not have static navigation to members accounts. When a member changes their nickname, links in navigation and browse.php change with it. So basically it applies to broken links.

But links change on dynamic sites all the time. Dynamic sites are pretty much all social networking sites.

yes, what he said...

 No, that's how it works. I just changed my username, from .com/user to .com/user1, I then went to .com/user and got the user profile doesn't exist. Google will now see .com/user's non existing page as a 404. I tried with "Enable friendly profile permalinks" both enabled and disabled.

I understand what you're saying about the links, but I'm talking about the the profiles that are already indexed in Google, no link to it needs to exist, the old profile URL is already in Google's index.

It's been a SEO debate for a long time, one that I don't want to find out the answer to the hard way.

Also, at this point, if I change the links from friendly to not so friendly, Google will start seeing the profile twice, and could be considered duplicate content, something else Google doesn't like.