Perhaps publications like Mondo 2000 and WIRED (and Boing Boing) killed Cyberpunk the way The Many Loves of Dobie Gillis stuck a knife in the beatniks of the 1960's. Not that they made fun of Cyberpunk, but rather they so overly-embraced it that they kind of unintentionally made a mockery of it (so perhaps not so much like Dobie Gillis?). That was the way I saw it in the 90's anyway.
Good point. Over-enthusiasm is definitely a way to make a cool thing uncool. There are a few contemporary writers who seem to labels themselves as involved with cyberpunk, but whom really make it all a bit juvenile and silly.