I run some very large forums, and the reason I'm now making a forum PaaS/SaaS play is precisely because of the above. Just Google for "Powered by vBulletin 3.8

I run some very large forums, and the reason I'm now making a forum PaaS/SaaS play is precisely because of the above. Just Google for "Powered by vBulletin 3.8" to see how many hundred thousands of forums are running old unpatched versions of forum software. Most people who run forums are into the topic of the forum, not becoming a sysadmin.