And the very reason why I so dislike Civ V: in Civ IV, you could use culture to literally take over the world, as your cultural influence could slowly convert other players's territories and cities to you. And the culture bomb was a magnificent thing.

In Civ V, at best they like you, and worst (and more commonly) your cultural achievements will just make them hate you even more.

Partly fixed in BNW with Tourism/Ideology mechanics. Sadly unfixed by the ease with which one gets a diplomatic victory on anything less than Immortal.