We do a lot of crawling various data sources. We spent over 3 years building a really great infrastructure to do this well. This is how we can present rank tracking for you and your competitors over time. The last time I checked, I think the number was actually over 500k... I should update that page!
"We track over 400,000 searches representing almost 50,000,000 results. "
Really? Where do you get this data? Apple is certainly not making it available (for obvious reasons).