Building a new site, how fast is too fast theory.

Based on Matt’s comments today, it looks like you can build a site too quickly. This makes a lot of sense; if you are going to spam Google it would be easy to generate millions of pages at the same time just throwing junk out of a dictionary. This is now problematic for the larger sites out there, if you can actually build a real site with millions of pages you need to slow down the release. But how fast is too fast and how slow do you really need to go? Generating a ton of content can be done, as mentioned with Wikipedia. They produce thousands of articles a day without issues.