Duplicate pages are bad. They cause a split in pagerank. Discount advice of anyone who tells you otherwise.

http://www.mattcutts.com/blog/duplicate-content-question/

I have a feeling the page rank of change.gov will be just fine, even if some googler has to hard code it.

I doubt they'll need hard code. This is a big new thing. I'm sure there'll be hella linking to this from around the Internet.

I posted the URL on Tumblr a few hours ago and already had 7 people reblog the link. That's one isolated instance. This'll be passed on quickly.

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.

It does. If you run a site, open up Google Webmaster console or Yahoo's Search Explorer and see for yourself.

I've done exactly that, and never found a difference.