Check out the taxes. If it's platted for a subdivision you might find that when they change it from agricultural to residential your taxes go up. They might go WAY up, even if the lots don't sell.
Blaine County, ID pulled this on some ranch land some years ago. There's a particularly scenic ranching area near the town of Bellevue. The county didn't want it subdivided because of the scenic value so they passed an ordinance limiting lots to 25 acres or more. Then, to raise money, they rezoned it to residential even though it couldn't be divided. The ranchers' tax rates went way up. It ended up in court, of course, and the county lost.
