If you're playing in a contest or are chasing an award, the question of "cheating" depends on the rules of the contest/award. Beyond that...if you feel a need to explain how your behavior is not cheating, it probably is "cheating". That being said, I think that a valid two-way QSO requires TX and RX to occur from the same "station". Usually, that would require the receiving and transmitting antennas to be close to one another, but I can see how low band enthusiasts with their own remote-controlled receive sites might claim validity. (Compare with professional marine/aviation HF stations.) Using a web SDR to "hear" a station you're trying to work that is inaudible at your station is a little skeezy in my book if some kind of bragging rights or sense of accomplishment is being sought...but it wouldn't matter if you're just trying to make contact for social chit-chat and don't care about whether it "counts".