fathom - 7:12 am on Oct 31, 2002 (gmt 0)

So once a site gets "fresh" crawled, why does it drop?

hmmm... I suspect that the previous "fresh crawls" are cancelled out by the new fresh crawl -- since these are not "retained" archives and new pages (not same) can be crawled each day.

Does it have to be re-crawled every day for it to show?

I would believe so. If your site is already in the previous monthly crawl your results would be back to normal ranked positions (unless someone elses page is fresh crawled -- above or below you.

Or does it drop because Google's serving results from a different data center?

Would again think -- just reverting to normal.

Reasonable guess work anyway, in the absence of a real inside Google knowledge, the king at his craft! :)

[edited by: fathom at 7:18 am (utc) on Oct. 31, 2002]