Interesting discussion at marginalrevolution which cites an article in the Times.

In a ruling last December that sent tremors through the not-for-profit world, the Minnesota Supreme Court said a small nonprofit day care agency here had to pay property taxes because, in essence, it gave nothing away.

The agency, the Under the Rainbow Child Care Center, charges the same price per child regardless of whether their parents are able to pay the full amount themselves or they receive government support to cover the cost.