Over the last two months all my sites (20) were down yet consistent in traffic.
Then last week I experienced a boost across the board. All separate sites all experiencing a very good increase in traffic.
Now - the last 7 days the drop in traffic has been steady and moving in a downward spiral, and yes, again across the board. What was significant that my anchor store (since 2002) was really dead in the water.
Site 21 (a political blog) with a PR 6 was beginning to show real signs of wear but it's recovering slightly.
Penguin, Panda, or whatever these sites are well monitored, all still very well indexed so maybe its the warm weather, summer fun, boredom but business is down, way down.