The range of those adapters can be highly variable. They're designed to make it through breaker boxes; if they didn't then they wouldn't be much use in a house built after the 1970's or so, when electrical codes started mandating much lower number of outlets per circuit than they used to get away with; if they stopped at the fuse box they wouldn't even go from room to room. They're supposed to stop when they hit an electric meter, but depending on the meter they can sometimes make it through that, and if they do... they will *probably* be stopped at the transformer, but typically there's more than one customer hanging off a transformer. So, yeah, I certainly wouldn't use them unless they have good encryption. The newer model HomePlug adapters are *about* as secure as WPA Personal (assuming you set a custom password, not just use them straight out fo the box), so if you're comfortable running a WiFi WAP you're not really less safe with the powerline adapters. But with the older standards/proprietary models, well... you could still make the argument that it's substantially harder for a "wardriver" to get into your powerline, so unless you live next door to someone who's both untrustworthy and is also using the same network equipment as you still have "security through obscurity" on your side.