[jfoster]

Has Google considered an indicator next to results for this type of case? A single red exclamation mark with further details when the mouse is over it, for example.

I'm aware of webmaster tools, but it seems not all webmasters are.

[Matt_Cutts]

We do include some information in the search results for cases where our users could be harmed, e.g. if we detect malware or if we think that your site may have been hacked. We've been exploring other ways to alert site owners that there's something important affecting their site.

But people do choose to remove their sites, so we can't always tell between a mistake vs. someone who genuinely prefers not to be in Google's index.