[Nightblade]

Quite often actually. If you ride the boat for a while, you'll notice that the big 'skips' the boat does generate the 'large warp detected' text.

I reckon it's because the positional information of your character isn't realtime updated. Imagine running across West Karana, and you start to lag hard serverside, but experience nothing at your computer. According to your computer, you're halfway across the zone, and when the server finally catches up, the next positional marker of your character is a HUGE difference from what it last knew, thus 'large warp detected'.