Blocking social networking at the firewall

My current client has blocked Twitter and Live Mesh at the firewall.  At what point are organizations going to realize that social networking is beneficial to project progress?  Now, I can no longer access my network of peers (well, I "can" but they are trying to prevent me), which has already provided me with many leads, links and ideas related to making this project better.  Now I can no longer access my repository of project files, where I am getting all of my templates and reference documentation.

What is the point?  Are they trying to prevent people from wasting time?  How about blocking YouTube?  How about uninstalling Solitare?  How about not providing access to the external internet at all?  There are a lot of clericals here, and many of them are temps, so why don't you just lock everything down?  If that is too draconion, how about two firewall profiles, one for developers and another for clericals?

This fear of the Internet is remarkable in this day and age.  Watching organizations (especially government organizations) try to bridge the gap of providing free access to information and keeping the temps from surfing porn is very frustrating for me.