Now here is an idea. Maybe Google and other search engines should look at forums, IRC, directories or any other type of 'mass meeting place' and see how they enforce their rules. Answer is simple...MODS.

Maybe Google should start a moderator program. The way this would work is people would fill out a form to sign up "Volunteer" to be a Mod and Google would accept or decline these people base on experience, knowledge, etc.
Now when someone reports a site, it would get put in a queue and then distributed out to a mod in random, or the next one in line. "The mods have no control of what site they get". The mod in turns goes to the site and determines if the report is justified and valid. They would also look at the severity of the issue. If the issue is not severe, then they would how the power to send a warning letter through email stating "Your site has been reported for such and such issue. We have investigated this issue and found you have violated such and such rule, bla bla bla and you have 60 days to fix the issue or risk being penalized or baned from Google" After the message was sent, it would then be put back in queue and held there for 60 days, after which it would be redistributed to the next random mod or the next mod in line. "Chances of it being the same one would be slim due to the number of mods". If the issue still exists, then it would be forwarded up the ladder to the existing team Google has in place now.

The mods would not have the power to ban or penalize anyone. The only thing they would have the power to do is send a letter of warning and forward valid complaints and severe complaints to Google.

With this mod system in place, it would do several things for Google.

1. Eliminate over half of the spam reports. "If you got a letter from Google, would you fix the issue?"
2. It would free up the Google team to deal with the severe issues and stubborn webmasters "the ones that have already been warned, but failed to fix the issue".
3. Does not cost Google a thing. Its volunteer.
4. Once this system is in place, it would put the fear of God, for lack of better words, into web developers who know right now that their chances of getting caught are slim to nil. With the system in place, their chances of getting caught are more than quadruple, preventing new web sites from being made in this manner.
5. It would give Google the ways and means to enforce their rules, which right now they do not seem to have. It would also save Google money because their team would not be investigating bogus reports, but actually taking care of issues.

I am not the brightest bulb in the chain, but I do not see why no search engine has put something like this in place. Learn from what works to fix what does not.

Before the question is asked, I will try and answer it. To try and get away from people sending bogus emails with fake links, etc., the email that the mods could send would not have any links in it. It would strictly state "you can log in to your webmaster tools and then click on spam report to see the status". With no links in the email what so ever, there would be no reason for people to try and emulate the site or send bogus emails.