If you live an old home or building, you already know the limits of WiFi. Despite the improved range of 802.11n coupled with improved throughput at greater distances? WiFi doesn't work magic. Buildings with brick or stucco-over-chicken-wire walls resist the charms of wireless networks, as do houses with thick wooden beams, cement elements, or with rooms spread out over many levels or floors.
Don't get me wrong. I've been extolling the virtues of WiFi as a way to avoid tedious wiring and pointless tethering since 2001. But in most cases WiFi works best in environments in which it's an obvious solution. When you start to layer floors, walls, and obstructions between a user (in a home or office) and the closest access point, you bypass the utility of easy and fast connections.