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While it is possible for an industrious programmer to get around this, it will be infinitely easier for the blogger to come up with clever ways to fool the bot and make the spammers life difficult.
MT did not provide an attractive alternative for the longest time. I don't even know if they ever did solve the problem properly (typekey is a joke imho) because I just shut off commenting altogether and gave up on the upgrade once they started with their new scheme.
Now Google calls them up and they just roll over and in a few days they accept this unilateral change to the web and deploy it overnight. Why didn't they work this hard to solve the problem in the first place?
Now I love a lot of things about Google. But what they do affects hundreds of millions of people at least. They have broken the web with publicizing pagerank. This will have an effect that no one can predict. I think it would have been more appropriate and cautious for them to discuss this new protocol publicly first.
In fact, all the search engines should work together with the body defining HTML. Participate as a good netizen, come up with some protocols to make the web better and discuss it the way html is discussed and implement it the way firefox is doing. It still leaves room for each company to do their thing better than the other, but let's keep the protocol strong rather than having one behemoth dictate the way the web works for all.