tedster - 5:13 am on Sep 20, 2010 (gmt 0)
I've seen the signs of it (whatever it is) on small business sites as well as enterprise sites. It's not all that common, but as the past two years of reports show - it's not exactly rare either.
It's not even clear to me if the "yo-yo" is part of the same phenomenon, but it seems to me that the only real way to throttle traffic is to change the rankings.
In our current thread for discussing Google Updates and SERP Changes [webmasterworld.com] there are a good number of people who mention that their traffic seems to fluctuate from non-targeted countries. So even though the total traffic stays pretty stable, slaes are on a roller coaster. I'm not sure if this mechanism plays in or not, but it does sound suggestive.
And then finally, there's the reports of sudden spikes. That sounds like long awaited good news for the business owner who has been "throttled". Maybe it is just that - a test of seeing what happens when the limiting factor is removed.
But that's just my guesswork for now. I do not work with any sites that are seeing this behavior, so I can't investigate it very deeply. That's why I started this thread - to ask webmasters who think that their traffic might be throttled to start a digging party into their analytics. After two years, it would be good to finally get somewhere solid on this topic.