Yeah right. You should definitely use a tool proactively that - was designed specifically for webmasters that have used spam techniques - is meant as a last resort after they have tried everything else to clean up their bad backlinks
I can only assume that you've never had a site either scrape your content or scrape the serps that included your site etc....
Our site has never done blackhat seo and yet I'm always finding links to us on questionable sites that we had nothing to do with being there.
I could spend all day going through our logs finding weird links to us... and Bill I am bordering on bordering on a psychosis.
Just the other day a bot got ahold of our site and before I spotted the spike they'd run through over 20,000 product pages. Sadly I dont just watch server load and traffic all day.