Microwave is anything from 300 MHz to 300 GHz. WiFi is well within the microwave range as is WiMax, GSM, UHF and VHF. None require line of sight. The only reason you need line of sight is keeping interference down and power requirements (both usually regulatory).

When I said microwave I meant specifically the microwave technology utilized by HFT (I've always heard it referred to as simply 'microwave'). I guess I was mistaken because I read that the microwave used by HFT beats out fiber because light travels faster through air than through glass and mistakenly implied that meant line of sight.