This is reasonably old news. And has been obvious pretty much since WebDAV began. But it's interesting to listen to Greg Stein talk about WebDAV, it's history and the reason why it was put into Subversion. At the moment if you want to go over HTTP for Subversion there's not any other option.
In the next version of Subversion, 1.7, there's going to be a new, not your father's, Subverison over HTTP. It basically means stop pretending to be WebDAV and fix it's problems. Perhaps the most interesting of which is that versions will have public URIs rather than going around and around using PROPFINDs. The WebDAV methods remain but it does look like the sprinkle it with some proprietary headers like X-SVN-Version-Name (which seems like a sensible way to send "the version I last knew about" information without the WebDAV tomfoolery).
As well, there's some other Git like features (svn patch to support Git's format). While I probably still favour DCVS for OS projects, Subversion still makes sense a lot of times.