They do realize, don't they, that the only way you can even really "share" that bandwidth is on a LAN...since each adapter's max bandwidth is much higher than what 90% of potential users will even have access to. Sure, I could install a Wi-Fi adapter into my desktop & tell it to "share" the connection between the Gigabit Ethernet & the Wi-Fi...except the router they both use is connected through a modem that will top out at 20-25 Mbps, nowhere near the threshold for Wireless-N, let alone Gigabit Ethernet, limits.
Not to mention that, at over $400 USD for the board alone, you're spending as much on the board as other people do on an entire budget build. And you're not going to ever see the benefit of the added networking speed. So it's essentially for wasted "bragging rights".