Sorry if ive made this comment before, but whenever a SE gets press because of their DB size the relevancy goes tumbling.
Northern got great publicity with the Science article a year or so back. Then eveybody realised their results were crap.
Same with Google. The moment they advertised their new 1B DB relevancy took a dive.
Fairly obvious that when you add a lot of pages all of a sudden quality control goes down. Not enought time to do 2 at the one time. Give me a slowly increasing size all the time with maintained quality.
Hope it dosent happen with FAST, but past experience may suggest it will!