Microblogging has become a business activity, people are concerned with their public appearance, with "building a personal brand" online rather than simply being themselves.
Convergence of personal and professional life - in terms of the immediate, ready accessibility of people - has meant that people have started to be a bit more guarded on the 'Net, or a bit more cunning.
This removal of anonymity is two edged, in my opinion, in that because people are more guarded, more cautious, they're more boring. Highly publicised outings of people on facebook, the scandals that erupt when employees gather together to bitch about their workplace - surprise surprise! - has highlighted the need to be a little more cautious in our online persona.
Where has the fun gone?