I think what actually surprised me the most was that the people not familiar with it were both well aware of who Dido was and yet surprised that this song existed. While Dido's song did come out 2 years before "Stan", it was only after "Stan" that Dido was all the sudden doing the tune on SNL and the late night talk show circuit and getting heavy airplay.
Oh, I was well aware of who M&M was, I just didn't listen to his stuff. Other than the little ""twist" at the end of the song, there is really nothing remarkable about it lyrically or musically to me, other than the inclusion of Dido's music in it, of course.
And when I heard Dido on the radio, etc, nobody was saying "Here is the latest Dido song, which also happens to be in an M&M song as well"....
I never really watched SNL or watched the late night talk shows - most were pretty stupid with little clever bits once in a while. I never found SNL to be as humorous as many others seemed to. I also didn't grow up with MTV or VH1 in the house - we lived out in the country and just got OTA channels. I really had no exposure to cable until college, and I was way too busy studying/going to class/doing things outdoors to spend much time watching TV.
Not everyone here is 18-20 years old and grew up watching 250 channels.