Google's latest Android release, 4.3 "Jelly Bean", is quite simple in comparison to past releases, but as always, with some digging you'll be able to find some interesting changes. One such change isn't obvious at all, and it might not be kosher with everyone: Wi-Fi scanning even if Wi-Fi is disabled. This might seem like the sort of feature that Google would rollout without telling anyone, but indeed, the feature is mentioned in the release notes:
"Location detection through Wi-Fi - use Wi-Fi to detect location without turning on Wi-Fi all the time."
For the most part, this feature is actually a good one, since it can help triangulate your location without the use of GPS, which could save on battery. But that said, it can be assumed that not everyone is going to like their phone or tablet scanning in the background, either for privacy reasons or lack of need, so fortunately, it can be disabled.
The option is a little hidden, however. You must go to your Wi-Fi settings, tap the three dots in the corner (or menu button) for the options and click "Advanced". Once there, you'll see options similar to those shown above. Don't want the feature? Simply de-click it.