There's a reason that, in places, the Stargate Project is considered the worst-kept secret in the universe, and that's because if you add up the people who have a canonical reason for knowing (at least rumors) about it, you have close to the total population of the Earth. :D So, yeah, I generally find it hard to believe when crossovers work on the assumption that nobody's ever even *heard* of it. (And somebody along the lines of Mulder or Hodgins who actually pays attention and makes connections? Probably knows almost as much as Landry does.)

I'm waiting for the story where somebody breaks the SGC's cover in the media, and the world's reaction is "Okay, so where's the part that's actually news?"

(It's almost as silly as writing something set in New Who universe where people don't know about aliens and alien contact. Not quite, but almost.)