Google is trying out a pilot program to alert site owners when we're removing their site for violating our guidelines. JavaScript redirects are the first trial, but we've also sent a few emails about hidden text, I believe. This is not targeted to sites like buy-my-cheap-viagra-here.com, but more for sites that have good content, but may not be as savvy about what their SEO was doing or what that "Make thousands of doorway pages for $39.95" software was doing. Personally, I think opening up a line of communication to let webmasters know when we're taking action is a really good thing--a site owner doesn't have to guess about what happened. But again, we're starting with a trial program.