I did not vote for Barack Obama, but I must say that this website is a great move. I pray that it is more than lip service and that they will use it to truly listen to all sides and respond in detail to the country on decisions they are making.
Yes, duplicate pages are generally bad, but nobody has demonstrated that having a www domain results in duplicate pages. It's a superstition.
I've the done tests myself, and never found a difference. The link you've provided suggests much the same thing -- as long as you're being reasonable in your use of subdomains, you're not going to be penalized by the search engines.
The country elected a Democrat, and a strong critic of the Bush administration. We now have a Democratic administration. Start getting used to it. It's unlawful to campaign from the White House (and thus I guess maybe from a .gov), but the campaign's over.