Currently LED lighting using AC power source require a reactant component such as a capacitor or inductor to limit current without dissipating power. With capacitance (most popular method) a diode bridge is also required.
If LED manufacturers made LEDs with two in a package back to back, the LED can be used in AC circuits with less fuss. Also mounting direction would be eliminated.
Each LED would only be operating in a 50% duty cycle thus increasing life span.