Google was deemed to have broken wiretapping laws when it scooped up unsecured wifi data while collecting images for Streetview.
The court ruled that no law was broken as the signals were being sent over the air, and therefore had no expectation of privacy. And since at that time the descramblers were sold to the user, there was no problem with modifying the hardware.
This is why they switched to leasing the descrambler boxes when they upgraded their system (and chose a system for which descramblers were not easily publicly available).
It always seemed a sensible ruling to me. Though I don't think anything has changed legally, I suspect the ruling might be different if such a case were tried today. :/