Once again, Mark Pilgrim says that we're acting like we're the first with problems, paying no attention to what's happened before us. This time, his essay is on weblog spam.
The low barrier is exactly the problem here. We got away with it (please, come post random links on my site which is well indexed, poorly managed, and open to unlimited anonymous contributions!) because we were collectively very young and naive and thought no one could hurt us. Now it’s like we’re turning 30 and being told we need to go on a diet and asking, "Well when can I go back to my old eating habits?" Um, you can’t. Your old eating habits don’t work anymore.
Pilgrim is a smart guy, and his essay has a number of good points in it. You should check it out.
As a side note on the topic of comment spam, one of the theories is that it's easy to target MovableType blogs because their comment forms tent to be so similar. What if instead of naming the comment fields, the MT application used generated keys? The labels would allow them to be useful to people and technologies for the disabled, but the underlying id changes might be enough to make the process more difficult for abusers. Just a thought.