Google is simply devaluating some Networks (blog networks, articles directories) and de-indexing/penalizing websites having DIRECT spammy links (scrapebox, xrumer ...).
Blog/Articles Networks
I would recommend that those who have been penalized list the SEO services and Networks they have been using, in order to find out which ones have been penalized by Google.
The solution in order to avoid drops due to "network devaluation" is to diversify your linking.
FYI, I haven't seen any drops in my websites yet. I am using all sorts of backlinking services (web 2.0, blog networks, edu profiles, article directories, social bookmarking ...). I also use scrapebox and xrumer services but only for my tier 1/tier 2 websites, not my money site.
Spammy Links
If you have spammy links pointing directly to your money site, then no wonder your website has been penalized or de-indexed.
Unfortunately, once this happens, you can forget your website as it will be in most cases considered in Google eyes as a "black hat spam" website. Doing strong quality backlinking from high authority websites IMO won't change anything. You might have a slight increase in ranking, but minimal.
These sorts of things happen quite frequently:
1) Had most of my niche websites penalized in June with a -50 penalty (due to spammy links I guess) and they are still with it. So what did I do ? Well I recreated new Micro Niche websites.
2) I was then making a solid 2500€/month with Adsense and scaling up, until Google closed my personal adsense account, and banned all websites from Adsense. So what did I do ? Well I have created more authoritative websites and am using my business Adsense account. I am also using diversified linking techniques as mentioned above and am avoiding all spammy linking services which would harm my money websites.
Meanwhile, I must admit that I have noticed that new websites (domain age less than 1 or 2 years old) seem to be more likely to see ranking variations when linking is NOT DONE PROGRESSIVELY. So make sure not to do heavy backlinking for a month or two and then stop, as Google will notice this and understand that you are trying to manipulate your search rankings.