Matt Cutts today announced that Google is starting a trial program to notify some webmasters if their sites have been penalized. To be eligible, one must register for the Google Sitemaps service.
From reading his blog entry on the notification service, it sounds as if they do not intend to notify black-hats of penalties, but only white-hats or people who are guilty of relatively benign or minor infractions.
I think this is a really great move by Google! Obviously, they're also seeking to increase registrations with their Sitemaps service, but this additional feature offering is making that overall program look increasingly worthwhile to me.
I met Vanessa Fox from the Google Sitemaps team at SES in NYC this spring, and I told her I was impressed at the new features she presented for Sitemaps: they are now providing webmasters with reports on various errors and impediments to spidering pages as well (errors are reported such as invalid formatting of robots.txt, etc). Previously, I hadn't seen a lot of benefit to using Sitemaps.
I think that we're in the midst of an ongoing sea change wherein the SEs are no longer considering SEOs to be pesky irritants, but beneficial collaborators. The white-hat SEOs, of course. I really hope this trial program is successful, and that more visibility might be provided for SEOs and webmasters.