Friend of mine interviewed for a role where they explained a problem and asked how he would solve it. He spent 90 minutes explaining possible solutions while they made notes. It's a pretty specialist domain so he knew others who were interviewing. After the interviews they pulled the position - I suppose no one will ever know for sure, but after putting their heads together and doing some digging they figured the whole set of interviews was put together to solve a problem the business was having, and it was just an easy way to get a bunch of solutions from very specialist / expensive people.