Certainly those are noble goals, which is probably why the system was defended by so many people who meant well, including the program's authors. The problem is that by doing so, the defenders are opening the door to a subtle, insidious form of censorship.
One might consider granting a pass to these sorts of things because they appear on first glance to offer a way for "the little guy" to strike a blow against the corporate powers. But this is a dangerous illusion... because both practically and ethically, anything that the "little people" can do, the "big people" can do, too, only bigger and with a huge marketing push. In reality, all that is being created is the ability to slap arbitrary content into the middle of a web page, and if any of these services ever becomes large enough, it would be co-opted by the very same "corporate" voices is was created to provide a counterbalance to, in the end only making sure that not only do the corporations own their own spaces, but anybody else's they wish as well. This isn't just theory; see Smart Tags.