Much of Pressflow's codebase was backported from Drupal 7, so its advantages will be available to all Drupal sites after the stable release of version 7 sometime early next year.
The change to Drupal 7 that make better http headers (now in Pressflow 5 & 6) will allow, afaik, for any reverse proxy, but varnish is definitely one of the easier to use.
All Drupal 5 and 6 sites can use these features by substituting the Pressflow core.
Now I'm wondering how the US government will contribute back to the Drupal project.
6 words in and there were so many errors that I couldn't continue to read. What is it with the PHP community and the inability to use English correctly?
More than one, but I avoid blogging in them to avoid "you're bad at language $foo". Knowing more than one language doesn't mean that your errors aren't annoying.
English is a language, a tool for communication. What he wrote is perfectly understandable by any reasonably intelligent individual who is fluent in English. I'm sorry if his English proficiency is not up to your standards, but I assure you that it is far better than your Flemish, or French, or probably any other language than English, which happens to be the one you learned as a child.
http://www.barackobama.com/ is run on Movable Type Pro, which is essentially the supported commercial version of the open source Movable Type. I don't recall the hoopla surrounding that choice. Buytaert's company Acquia helped develop whitehouse.gov. Perhaps some of the development that went into whitehouse.gov may end up back in open source, but I wouldn't bet on it.
I would hope that the White House would apply their cyber-security experts to the problem of securing Drupal and contribute their changes back to the community. ;)
You have to enlighten me how it could be a different physical server and yet be the same hard drive ?
Unless you are suggesting they use ATA-over-ethernet or something like that to share the same drive.
Or maybe you meant to be worried that they might use virtual machines where one is running the .gov site and the other would be mail server or something like that ?
At the volumes of web traffic they receive there it would surprise me if they only had one server to do just whitehouse.gov, especially if they're using drupal.