#1: Mismanagement of site resources so it becomes too slow or troublesome to use. One example was a site in a hobby niche I like, they widened the format ridiculously to monetize with ads, I got side scroll. Second the entire site is so mismanaged technically, it takes at least 1-2 minutes to load every forum page. I'm outta there and rarely return ("Do I feel like a nostalgic blast to the 90's today, stare at white pages for up to two minutes?")
#2: Rules and enforcements that apply only to those outside the "inner circle." Although it's never been directed at me, I've been to many forums where any newcomers are beat senseless with flames to "search before asking" and the like, rules enforced swiftly and mercilessly, while the inner circle can do just about anything they want without a care. So all the "little people" leave the royalty to their utopia.
#3: Ads, ads, ads. Sneaking ads in between posts in threads and the like has annoyed me off of many boards.
#4: "Log in to view answer" has stopped me from even joining some (O.T., but while we're on boards and what kills them . . . )
#5: Same old jokers, nothing new here. And the jokers are generally not interested in anything engaging ("if it's not about me, it sucks.")
#6: General lack of real organization or freshness, though an initial search may have brought me there, going back on a regular basis doesn't stimulate and enrich.
#7: Time. I have to pick and choose my priorities, I'll say that this is the **only** board I visit daily, sometimes twice, seems like every time I read a thread here I learn something. I just don't have to time to dedicate to multiple message boards.
#8: Personal reasons, no longer interested in the topic.