This is the IRS picking a large easy to get target that gives them exactly the thing they want. It's much easier than attempting to mine the county-by-county land use records that are in disparate formats over the rest of the country. Gifts and other non-market value transfers are in fact coded in our county, and that info seems to be public record so it's quite possible that they got that already for our million or so population compared to the 37 million in Calfiornia they're getting in one swell foop.