It's fairly obvious that if you change something like the Pompeii business, it'll have massive great consequences on the future. I could watch something like that happening and only think "Hmm...that really sucks."
I imagine it'd be different if my family were currently living in Pompeii, or something, but they're not. So happy days.
However, in the world of Doctor Who, they don't have Doctor Who on TV, so maybe they wouldn't understand all this time travel lark as much as we do.
