This supports a theory I have that the behaviour of an online community is heavily influenced by the software it runs. So for example in a blog that runs WordPress with regular comments, everyone takes their lead from the blogger: if he's thoughtful and polite, so are they, if not, not. (The subject matter has an effect, but less than you might expect.) If he happens to be running Disqus comments, the blogger has less influence, because people lek for 'likes'. Metafilter (my favourite community site) uses a layout and moderation system that you won't find anywhere else, so the community is likewise unique. And 'forums', usually running either SMF or phpBB, all resemble each other in that

• Lots of people talk smack
• Even more people act very defensively
• Many don't read more than three or four comments in the thread before they reply. I certainly haven't read all the comments in this one. A side effect is that there are more outright dumb comments, although intelligent ones may or may not exist alongside them.
• Smileys everywhere
• Mods make a lot of explicit rules and 'sticky' them – stickying itself being particular to this sort of forum.
  
  • These rules become more arbitrary over time.
• Your reputation is very visible and significant, thanks to the per-post sidebar on the left that says how many posts you've made, and even what 'title' you have.

Instituting a rule that people without established rep have to post in a forum that no-one, including the posters, reads, in order to prevent 'spam' – the lurk requirement may reduce spam, but the posting requirement won't – is a perfect example of this. Ironically when I attempted to post to another thread fifteen minutes ago it was in order to point out that Mark Karpeles' motto of "php can do ANYTHING!" should probably have tipped more people off that MtGox wasn't the most secure of sites. The way you talk, the way you code, the software you choose to run, all both say something about you and affect your actions and nature.