I think at the moment I'd rather allow gates than not, on the basis that most of the ones that are actually locked are usually dead ends / cul de sacs anyway, and if someone's trying to route down there they probably live there or something, rather than using it as a through route.
The ones that I'm suspicious of are "service roads" that are blocked off as the security of a private business but there's a through route to some cycle path round the back of a warehouse or something. Any examples of impassable/locked gates on a surfaced through route much appreciated -although I suspect (and hope) these are rare.