In my previews two posts about my run-in with StumbleUpon, I talked mainly about the number of visitors that ended up going to one of my sites.
I concentrated on the numbers of visitors as, according to the monetization (sic) community anyway, its all about visitors; the more you have the more money you get. Unfortunately for me, it turns out that this was the exact opposite. Instead of making a few extra dollars for a couple of days during the peak in traffic, I actually experienced a drop in click throughs for the next month!
To me that sounds kinda counter-intuitive. Lets take a look at the graphs:
The top graph is the real number of click throughs a day (not the percentage!), and the lower graph is impressions across all of my sites that run Adsense ads. The thick line is the line of best fit (showing a nice steady increase in traffic and money!).
As can be clearly seen, around about the 22nd September the StumbleUpon traffic arrived for one of my sites. It died away again really quickly (see the full write up about the traffic profile here: StumbleUpon for fun and profit - Part 2: Results).
But what is really curious here is the uncharacteristic drop in click throughs for the following month across all my sites. As you can see, click throughs are way below the trend up to ... are you waiting for this ... the 22nd October, i.e. exactly a month after the StumbleUpon traffic!
Does Google check referrers?
So this lead me to thinking - is Google checking the referrers before it decides which adverts to display for my pages. Maybe if it detects a lot of "low quality" traffic from sites like Reddit, Digg, StumbleUpon etc it puts your account on a black list, and then puts up some uninteresting, low paying adverts that no one is interested in to protect its advertiser's budgets?
That seems a bit far fetched maybe, perhaps it is the case that Google simply monitors the number of impressions and, upon detecting suspicious activity such as a huge spike, sends out the uninteresting, low paying adverts as above?
Whatever happened,
exactly one month later my click throughs were back up to a healthy level. Unfortunately I didn't notice this happening at the time otherwise I might have disabled my adblockers and had a look at what adverts were actually showing - hopefully next time I'll catch it in time!