SEO is mind-boggling. Many years ago things were much simpler. But just like most things today, SEO is more complicated than ever. And for what ever reason people still feel like getting backlinks to their website is the absolute miracle, magic trick of SEO.
It's hard to say how much value back links even hold today, I'm sure it's still weighted; however, there are many other elements that play into SEO. One thing is for sure, low-quality back links pointing to your website is still BAD!
So that being said, if you think your website took a hit due to low-quality back links, Google now offers a way out and a way to get your website back on track.
It's a new tool in Google Webmasters. You can learn more about it on Google's webmasters blog: