There is one reason why I can think that this incredibly bright Alexander McQueen Metallic Wallet would be absolutely necessary. That would be if I had a gigantic bag with an ink black lining filled to the brim with items. In that (rather rare) case, the crazy color would be useful because it would be easy to spot the wallet among all the other things in the bag. It would probably glow in the dark, so no worries: you can grab it from the bag if you need it suddenly in a pitch-black area.
It can make a great clutch if you are into extremely, extremely bright metallics, or if you need something to add a burst of color to an all-black outfit, but I really like the idea of it with charcoal grey. I personally go out of my way to avoid extremely bright metallics like this in favor of muted leather metallics in dark grey or gold, but this is definitely a niche bag- I know many a person who love bright colored metallics an pull it off well. All I can say is be careful, because it is practically blinding. Buy through Zappos for $479 on sale.