Well to clarify a bit it won't void a warranty on anything outright. Sure they won't warranty your aftermarket intake but anything else can still be under warranty. It's only if they determine, which can differ so widely from dealer to dealer and the mood they are in lol, that it has caused a problem on things related to it.
For example, your MAF goes out under warranrty. Sure they can say its caused by the intake but if it was already a malfunctioning part with nothing to do with the CAI being installed then they technically can't just say you aren't covered because you installed something like this... unless of course you install an aftermarket turbo or NOS...then thats a whole different story lol.