We had a hackathon at my work. However it doesn't match the description here. The manger in charge solicated ideas from the organisation (to be fair including the IT department). A small group of managers including the board looked at the ideas and pruned them down to six. We were broken up into teams and given one of those ideas and then we could go forth and code for a day and a half. It was a useful exercise but the IT department already has a backlog of work that people are pushing for and while some ideas might get cycled in over time (and it was nice to use some new tools) it wasn't somethig that threatened to overtip the cart.