Maybe Google should start working with security firm so that once their bots crawled on a leaked database they will notify the website owner immediately.
In that case, it seems far more easier for developers to put in honeypot emails in the databases and constantly query search engines hourly when those become available.
That is assuming database gets released, let along exposed for indexing.
If you don't want something indexed, don't put it on the web. And sure as hell don't link to it.