jammy8891 - 8:58 am on Aug 1, 2013 (gmt 0)
Let me speak from experience here. I took on a client a few months ago who had received the widespread Jul WMT message and took no action. Their traffic saw a slight upturn immediately after receiving the message but from then on it was on a downward spiral.
When they started working with me (April 2013) I immediately took the WMT message to mean that they had some bad links and even if the site was not under penalty as such, these links would still be harming performance. After a lot of link removal & disavowal, I submitted a reconsideration request, which failed. The message back was along the line of "Site still violates quality guidelines". A bit more link clean-up, a second reconsideration request, and the message back read "manual spam action revoked".
So the way I understand it is that some manual action had been taken against the site - definitely against some of the spammy links coming in, and also likely against the site in general (basically I believe it was "flagged", with ongoing link devaluation and very close link monitoring). We needed to get this flag removed, hence the link removal and reconsideration request. Anyone who has received this message should definitely do some link clean-up and submit for reconsideration, as it's a pretty blatant warning from Google.