Wilburforce - 5:15 pm on Aug 19, 2013 (gmt 0)
this suggests it is a deliberate 'attack'
I suspect not. I personally believe that Google's focus really is on spam/manipulation, which is an endemic problem.
I am fairly certain they won't have paid much attention to my particular industry, in which the whole of page 1 for several of the terms I monitor has changed population completely a couple of times in the last two years. Actual people at Google cannot have a web-wide, industry-wide view, and probably monitor a basket of industries and terms which will include "problem" industries like adult and financial sites, and a few others to make their basket "representative".
The effect of algorithm changes on a lot of posters here, including myself, has been negative and substantial. With each update/refresh, my own site's position - still page 1 on all other engines - deteriorates further.
I don't know what terms others monitor, but the effects I see are all on short (one- to three-word) terms, and for what it is worth I think Google's performance on longer phrases has improved and is better than Bing's. Their penalty target is keyword/key-phrase searches (these are the spammer's target too). The results I see suggest they are getting it badly wrong, but that may not be what they see at all, and their focus will be on the searches with BIG numbers, and they have the data to tell them what these are.
I think industries/search terms that are relatively infrequent - my own main key-term only gets a few dozen impressions/month - are not in their radar at all, and some will certainly be affected more than others. The most likely explanation in your case is that some factor common to the industry has resulted in collateral damage that from your pespective looks widespread, but from Google's may not even have registered.