An interesting thread at WebmasterWorld reports Slurp entering site through Overture Ads. The thread creator reports this behavior only on Thursday mornings.
On four seperate days (all Thursday mornings) we had Slurp bombarding our site for about an hour with over 1000 requests, all of these being referals from our Overture Ads
An other member confirms the same activity on his site;
show an abnormal amount of Slurp activity between 07:00 and 14:00 every other Thursday (as well as on a couple of Saturdays). Each time it's about 1,000 visits from the Inktomi IPs.
The interesting portion is that the other member reports that the Inktomi bots are coming through on ads that they pay for but are not being charged to them. BrotherAl says, "Some of the keywords used by Slurp to get to our site have never been clicked according to Overture's stats, so we're pretty sure this activity isn't being charged for."
Can it be some sort of destination page verification process?