tedster - 1:30 am on May 26, 2008 (gmt 0)

I'm fairly sure that Google likes to see links and pages added in a natural way, which would mean spread out.

Yes, that's one kind of "natural". But it's also a common practice to develop new site areas in a test environment and launch the new area all at once.

Depending on Google's previous spidering priorities for a domain, going from 200 pages to 12K in one jump could mean relatively slow spidering, too. Google's crawl team has their own logic for how to allocate spidering resources.