jimbeetle - 2:15 pm on Oct 29, 2012 (gmt 0)

As implied in Google's initial post and the accompanying Matt Cutts video, Google expects to see some unnatural links taken down *before* using the disavow tool:

[searchengineland.com...]

Question: What if you don’t try to remove links? Given what a pain it is to get links off the web, why wouldn’t someone just use disavow? I know Google recommends requesting link removals, but from a technical standpoint, if they don’t do that and just disavow, it’s pretty much going to work, right? Answer: No, I wouldn’t count on this. In particular, Google can look at the snapshot of links we saw when we took manual action. If we don’t see any links actually taken down off the web, then we can see that sites have been disavowing without trying to get the links taken down.

Also, since Google included comments to document failed attempts to take down links in its first sample file, I'd consider this to be a "strong suggestion" for webmasters to do so as well.