My wife is thinking of giving up her blog. A service which allows her to track her favourite hobby came online this year and has been adopted wholeheartedly by its target audience, thus diminishing the blogsphere and she feels she's better off contributing to this as the number of visitors to her blog diminish.
I'm getting regular invites for professional social network, Naymz, but I ignore them since I already have a thousand contacts on LinkedIn.
Of course, there are winners and losers in any medium, and, as Friends Reunited showed, a winner can rapidly become a loser. However, the overall problem is that there are only so many hours in the day.
And the reality for the English speaking web is that the online marketplace is reaching saturation; any growth has to come from eyeballs moving from other leisure activities such as gaming and TV viewing. The 'growing pie' has become a 'shifting pie' and everyone's clamouring for a bigger slice.