Hi,
I know there has been some discussion on this before. I just wanted to add what I just did.
I have a casino site that ranks OK and makes a little money. Nothing big but it was slowly climbing each month.
Recently it tanked. I thought it might be because of the Google updates.
I checked the backlinks and I had over 600 low quality sites linking to it from African domains.
I don't do any business in Africa and I have no customers from there.
The anchor text was some of the keyword phrases that had been making me money.
They were all multiple redirects and some of them went to virus laden sites.
They all linked to my site within a one week time period.
I just sent a disavow list to Google with over 600 links.
Just one of those things to keep up on.