I've always wondered if YC would fund ideas that were based on scraping (like this one) and therefore liable to receive this sort of letter at any time

Now I know! Usually there is some sanctioned way to get at the data that you're scraping, but it's impossibly expensive. Looking at you, ATPCO... (raw airline fare data)

Kudos to these guys for sticking with their idea and finding another way to feed it data!