Could Matt do that - sure. Would he do that straight away, faster than the results can be captured, or does he have constant monitoring of his page - I doubt it. Still - nobody even tried as far as I can tell.
I don't know. I'm sure tons of spammers already target Matt's site (they all hate him). Google probably already has some kind of special exception for him.
Spammers targeting mattcutts.com doesn't make sense. You are assuming Cutts plays the same SEO-game, and has the same "I have to be number one for my keywords" ambition, which isn't a given. All spammers do by targeting him is giving his spam team more data. mattcutts.com is just bait, no downside if it gets negative-SEO attacked, lots of upside.
The more negative SEO that happens, the more data that gives Google. Overtime, the negative SEO sources will be over-saturated, offering no benefit for either positive or negative SEO.
Driving down the positive and negative value of links makes all SEO link building efforts consequently worthless. Which in turns increases the importance of other ranking factors.
This is a natural evolution, in tiny tiny steps Google is nudging people into playing it's game - producing websites that have content. SEOers are slowly falling into line building private link networks, paying people to write content, afraid to spin/rehash existing content because it might leave a fingerprint Google can detect.
You are assuming Cutts plays the same SEO-game, and has the same "I have to be number one for my keywords" ambition, which isn't a given.
People do have emotions and act on them from time to time. I don't think it requires any assumptions about Cutts's ambitions, but rather about how much effort it would take an annoyed spammer/black-hat to point some of their tools at the highly visible source of their frustrations.
Driving down the positive and negative value of links makes all SEO link building efforts consequently worthless. Which in turns increases the importance of other ranking factors.
You have a highly optimistic take on this. I think history generally shows that staying one step ahead of criminals/spammers/up-to-no-gooders is a never-ending struggle that does not tend towards positive resolution.
What "other ranking factors?" If you knew what those were, or even knew for sure they existed, the SEOs would too and they would be exploiting them. It's an entire industry whose sole purpose is to understand and game Google's rankings, and just as all this fuss about negative SEO shows, they're not losing.
"I don't think it requires any assumptions about Cutts's ambitions, but rather about how much effort it would take an annoyed spammer/black-hat to point some of their tools at the highly visible source of their frustrations."
highly visible only in SEO circles. The rest of the world could hardly care less. It certainly wouldn't make any mainstream news bulletin.
"I think history generally shows that staying one step ahead of criminals/spammers/up-to-no-gooders is a never-ending struggle that does not tend towards positive resolution."
Google are not one step ahead, they are always one step behind, reacting to the next thing. One step ahead is dealing with a problem before it even becomes a problem - in chess they call it prophylaxis - defending before you need to defend.
History generally shows bad things prevailing by people sitting back and doing nothing.
What Google have done with spammy link penalties is to change the game SEOers are playing. It's a classic advice of if you can't win this game, change the game. (Similar to Honduras' World Cup football efforts: if you can't beat 11 men, beat 10).
Although they could certainly have something in their algorithm that says: "This site as always been very good and now all the sudden it's getting a bunch of spam links. Ignore those links." It's not like you are going to use negative SEO to bring down a wikipedia but I could see it happen against sites that would be a Pagerank =< 6.
