The higher the frequency, the smaller the item required to block it. Some commercial items using the amazingly high frequencies use technical trickery to get round the problem and effectively go round corners, but that, as far as I am concerned, is firmly in the realm of magic.
If a 5.8GHz receiver only had one antenna wire this would not apply, I would guess that it would be line of sight only, no interruptions. I haven't spotted any model use of this band, but I expect it will come when smartphones using it become more common and production of the hardware becomes mainstream, and thus cheaper.