Hi Lars,
As I said in July, this problem is solved,
If you setup the preferred domain from the beginning then the other host names never appear in google search
http://www.mojoportal.com/forcing-a-preferred-host-name.aspx
If you force the preferred host name at the beginning when you launch a site then you will never have a problem, the problem only occurs after users have bookmarked your pages with the incorrect host name or if google already indexed it with an incorrect host name then it is possible someone will land on the non www link from google or a previous bookmark
If you set the www hostname as preferred and only submit the www site map to google you will have no problems. The problem only arises if you let users use more than one host name, if you force it to use just one from the beginning you avoid problems.
If users type in a different url in the browser and it redirects it has no effect on google. What you need to avoid is having any links anywhere that use the incorrect urls so they never get crawled by google. Forcing the preferred host name in the beginning solves it as long as you don't manually create incorrect links in your content.
If you didn't lock it down in the beginning and you already have a bunch of incorrect links in content that google crawled it becomes very difficult to solve without something like url re-writer to create permanent 301 redirects
I have never had any problems with mojoportal.com vs www.mojoportal.com because I've been forcing it to use www.mojoportal.com for a very long time.
Hope it helps,
Joe