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I've seen my (non-keyword-domain) disappear and reappear, move up and down the serps for many days before finally settling down.
That's why they call it "The Dance" ;)
Incidentally, do a google search for "Welcome." How many sites do you estimate have that term in their title tag? So, all things being roughly equal let's examine the serps:
The number one ranked site is a PR9. The search terms only appear within the inbound links.
The number two ranked site is a PR10. The search terms also only appear within the inbound links.
A PR9 beats a PR10! I've been following this "welcome" search and this is the first time I saw something like this. But it may be a temporary anomaly.
What this seems to say is that the brute force of inbound links with relevant anchor text is enough to buoy a site to the top of the serps, with greater weight than "on the page factors" and greater weight even than PageRank itself.
But this may yet shake out once the database gets integrated and sorted.