[kevincox]

While you maybe "shouldn't" be indexing collections often (which I also don't agree with, there is a reason that we have more collections then linked lists, lookup is important) even just getting the size of a collection which is often very related to business logic can be quite annoying.

[AndrewDucker]

For data that needs to be looked up mostly I want a hashtable. Not always, but mostly. It's rare that I want to look up something but its position in a list.