I don't know how to <i>solve</i> the problem, but I have thought about it; some thoughts:<p>The computing industry seems to keep repeating cycles with local and remote processing - thin terminals and mainframes, then the desktop PC, now "The Cloud" is mainframes 2.0, then mobile apps are starting to bring native code back to the user again (although many are tied into the cloud) - similarly, online communities keep alternating between distributed (BBSes + IRC), centralised (myspace, AOL), distributed (forums + IRC again), centralised (facebook + twitter). As such, the churn of users from one system to another is pretty much constant. (There are many reasons for users to move from one system to another, but this is the one that I've seen as an inevitable constant since the internet began, and other reasons are different each time).<p>How does users moving around relate to quality of community though? Perhaps I'm being subjective and biased, but it seems to me that the highest signal to noise ratio happens at the front of the wave, the masses with the pop culture are the middle, and the ocean of spam trails behind. As such, if we assume that users will move from one system to another no matter what, the degredation of community at a given location is inevitable.<p>Taking slashdot as an example - the technical side of it, while not perfect, was fairly good and did a fine job back when a handful of technically-inclined people used it; but when it became overwhelmed with average people, there's nothing the system could do to stop it (I don't think HN is immune to this either, it just happens to be at the front of the wave right now). Also in the case of slashdot, the editors started treating the average people as their target audience, which accelerated the decline...<p>Also, thanks to things like Ubuntu, slashdot's niche of "linux users" stopped being a niche, thus opening the floodgates - I find that communities are generally better when you need to put effort into finding them, rather than them being the default that the lazy people go to for a popular subject (note that this isn't quite hipster sentiment - that would be to say the subject <i>itself</i> becomes worse when it gets popular).