Over the last few months, Stephen Downes has made several references to the importance of owning your own domain. I fully agree. The contributions that I make to blogs, social networking services, and Twitter are under the control of the organizations that build and develop those tools (but I host my own sites/domains for posts/discussions as well). Generally, companies need customers, so they try to walk a line of creating a space of trust and attempts to commercialize efforts (and legal issues as well). Trust is needed in order to foster a growing network. However, sometimes things like this happen: Google deletes music blogs.
For a detailed exploration of trust, see We are Media. Do we Trust Media?. The focus is more on peer-peer trust, but does consider the low levels of trust with media companies as well.