If I were Google, I'd
1. Consider everyone who uses Webmaster Tools a SEO spammer. Maybe establish a list of manual exclusions, vith reviews triggered based on daily traffic.
2. Randomly apply and remove penalties to their sites (small number of sites actually).
3. Maybe randomly send "unnatural link" or whatever other notices (about something which webmaster have no way of verification).
4. Have Matt Cutts or whoever the PR person of the spam team is, to tell about 30..50% truth and the rest weapon-grade drivel. Maybe even including some verifiable facts.
This would have resulted in a utter and complete chaos in SEO world.