I've been noticing spikes in eCPM, but not thinking too much about it since its a rather minor channel with light traffic. I'm not talking a little bump: these spikes are in the mid-hundreds of $.

Tonight, while looking over my charts, I noticed the spikes are appearing regularly. A little tracking revealed that they always occur on a Friday, Saturday, or Sunday. For one day; never a series like the weekend, perhaps.

There is a corresponding increase in CTR, so I'm guessing a heavy duty advertiser is coming in to the market, and that the ads must be pretty compelling.

So I'll now be tracking advertisers/urls/sites in this channel on Fri/Sat/Sun.

I'm not complaining, mind you. But I can't figure why someone would come into the market --or drasticaly increase their bids-- for just one day, especially near the weekend. Why not 2 days? Why every week (for about three months)? BTW, weekends were my weakest 2 days of the week in this topic niche, which makes this even more confounding.

This channel is a sub-topic of a large super niche based on a health subject. No other sub-topics/channels are effected. I am well familiar with eCPM spikes in new pages and channels that receive only a tiny amount of traffic, but I don't think thats the case here. I've got over a year's tracking as data.

Any thoughts about whats happening? Any ideas on how this might be leveraged?

Thanks much in advance.