There are times when having your own collection of objects can come in handy in an application. Say for instance you want to create an list object that you can add or remove items from and then do something with the collection as a whole. Sure you could pass around the Generic List object of your given object type and create a method that does what you want and accepts the generic list, but that seemed rather disconnected to me.
Recently I had the need to loop through a collection of repeaters on a page within a website I was working on. Here was the situation, we had two repeaters on an ASP page that displayed items that were owned by you in one and ones that had been shared with you in another. Before rendering the repeaters to the page we needed to determine which repeater item in either of the repeaters was currently selected so that we could set the style of the repeater item to highlight it.