Source : Free On-Line Dictionary of Computing

smoke and mirrors
     
        Marketing deceptions.  The term is mainstream in this general
        sense.  Among hackers it's strongly associated with bogus
        demos and crocked {benchmarks} (see also {MIPS},
        {machoflops}).  "They claim their new box cranks 50 MIPS for
        under $5000, but didn't specify the instruction mix - sounds
        like smoke and mirrors to me."  The phrase has been said to
        derive from carnie slang for magic acts and "freak show"
        displays that depend on "trompe l"oeil' effects, but also
        calls to mind the fierce Aztec god Tezcatlipoca (lit. "Smoking
        Mirror") for whom the hearts of huge numbers of human
        sacrificial victims were regularly cut out.  Upon hearing
        about a rigged demo or yet another round of fantasy-based
        marketing promises, hackers often feel analogously
        disheartened.