On the plus side, most people now have been exposed to a forum before, so it's more now a problem of migrating cultures, rather than people just learning what a forum is for the first time. Which was the case for the the usenet September 1993 example that created the phrase "Eternal September" after AOL came in to existence and flooded usenet.

Now it's people who have forum experience migrating to other forums. Which has positives and negatives. People are more sophisticated in their understandings of forums in general, but also some people bring bad habits from other low-quality forums.