One of my networks lost almost all it's google rankings 4-5 months ago. The sites were not banned, but they were not even in the top 1000 for search terms that they had been in the top 10 for for a long time.
Then a few days ago I noticed that there was a sudden surge of traffic to that network and what do you know. Almost all the keywords those pages are optimized for, have #1 spots in google and the traffic is exploding.
I don't get it, but I like it when the traffic is flowing my way.