I was just reading a blog article about the security of Google+, and the page mentioned a header I hadn't heard of before: X-Frame-Options
I'll let the Mozilla docs do most of the talking, but suffice it to say this header allows you to say whether or not a page is allowed to be used as part of a frame (there are options to deny the ability outright, or restrict it to pages from the same domain). See also the informational Internet-Draft.
Given that frame busting has been a feature of Stack Overflow for as long as I can remember, doesn't it make sense to include this header as an added layer of protection for those using a somewhat recent browser?