[shameless_1]

> ... and may still be here but undetectable to our current technologies.

I recently saw a nature doc where they were raising Panda cubs. Because the species isn't doing that well and breeding in captivity is problematic they try to keep them unfamiliar with humans [0]. Keeping them undomesticated, so to speak. The caretakers wear Panda costumes every time they have to interact with the cubs. They do the same when raising endangered birds: hand puppets reduces imprinting with humans [1].

In that respect, I think it's overkill for alien tech to rely on advanced tech to make themselves undetectable. Look up at the sky. See those Boeing and Airbus planes? That's how easy it is. Disguise your spacecraft as a reflective metal tube that leaves a trail of water vapor and you're done.

Disclaimer: I don't actually believe they're among us.

[0] http://www.youtube.com/watch?v=_fXBRKWmICU

[1] http://www.youtube.com/watch?feature=player_detailpage&v=XNk...

[sejje]

That's how easy it is to fool us, that doesn't mean the standard would hold true for other potential civilizations.