A couple of years ago, when digg was launched and wasn't anywhere as popular as now, it was quite interesting to have a look there. It was more or less like an assortment of random stuff, quite oriented towards technical matters, so was an easy way of reading different things without having to jump from one page to another.
Some time after, lots of people discovered about the site, it got popular, and people began to submit lots of content only for the sake of increasing traffic to their websites. It was when we began to get bombarded with the advice of so-called experts advising on how to title a blog post with the only purpose of inducing people to click it, bookmark it and all that, and so we ended with these symptoms.
More or less at the same time, del.icio.us discarded their old style front page (which used to show the recently added bookmarks) and chose to show the most popular posts. You could still look for the just-posted stuff but it wasn't that accessible. This led to people coming to del.icio.us, seeing the popular stuff (which usually was designed with the purpose of being bookmarked, see above) and bookmarking it again, which made it rank even higher.
Parallel to all this, bloggers with a desire to blog about fresh news kept using digg and del.icio.us as their main sources. This creates a feedback loop in which stuff which was already popular gets even more popular and can even manage to appear in more traditional websites such as Slashdot or The Register.
I thought that the trend would stop at digg but unfortunately it didn't. New websites flourished, based on the same pattern, such as dzone, a digg for developers. As expected, at the beginning it had very good content, and now I'm seeing more and more of those "50 must have tools for developers", "4 languages you need to know", "15 css tricks that increased my sex appeal" or "30 tutorials for free" on the front page one day and the next one as well.
At the end, mediocrity gets promoted to an unforeseen level of popularity, internet is polluted with crappy wannabe content, and I sorely have to lament the demise of yet another website which looked good.