What's behind the question Les? There are no state secrets on this forum, nor any financial transactions. The worst that might happen from a determined hacker is that they may frape you. Some people may get an annoying pop up from their browser from time to time stating that the site is not https, but compared to a conflict warning whenever a remote off-site image or non https page is linked in a thread, which is worse or more annoying I wonder?
The subject is hot at the moment because of Google's bully boy tactics which are intended to panic everyone into obtaining SSL certificates - but apart from that, as I say, what is behind the question Les? There are huge issues on a vBulletin platform in converting from HTTP to HTTPS, and if it is a genuine concern, which can be backed up with real evidence or argument, then of course, efforts to change to HTTPS would be made.