gouri - 10:03 pm on Jan 13, 2013 (gmt 0)
I'd call it a "scraper" rather than a spider. But I doubt it was human. If you go to the log files, you will probably find they came from a limited IP address range.
I am able to see IP addresses for a period of time; I can't see them for a particular day. That has made it tough for me to determine where these impressions are from.
Do you think that this was some sort of scraper bot that visited the pages of the site repeatedly in a short period of time?