21 months ago, Google launched the disavow tool and SEOs have been eating it up.
However, still many webmasters use it in fear of being slammed later.
One such webmaster posted in the Google Webmaster Help forums saying the disavow feature is "killing my site."
SO LONG STORY SHORT. I decided to disavow these links because they are not very good and I don't want them to represent my website, or my writing style. That was the BIGGEST mistake EVER! My site went from 500 to 600 hits per day to 40 to 60 hits per day. This all happened the day after I submitted the Disavow!
Supposedly he uploaded his disavow file on June 25th and his rankings tanked on the 28th. Many are saying that Google's disavow tool doesn't work that fast, that it might have been something else.
We did report on an unconfirmed update on June 28th that may have impacted this site, even without the disavow being related.
Often, since there are so many variables to rankings, it is hard to say one action resulted in a specific outcome. Most seasoned SEOs and webmasters know this.
Forum discussion at Google Webmaster Help.