Materially, this is something that concerns beancounters, really. I think Nintendo is rich enough that it can peel off those dollar bills and slap 'em down for wiiu.com, one hundred, two hundred! But they should have seen those fighter planes. This isn't callofduty11.com or halo29.com, or any number of sequelized domain names your garden variety cybersquatter should register. This is something registered June 7, 2011, which was—ding, ding ding!—the day Nintendo revealed to the world that trademark. A trademark it, presumably, knew about a day or two before. Whoops.
[Correction] Fusible in fact says wiiu.com was registered in 2004, but is not believed to be owned by Nintendo. nintendowiiu.com - Registered at Namecheap.com is the domain that was registered June 7, 2011. In either case, neither domain is believed to be under the control of Nintendo.
So (shameless plug!) that's why you watch Kotaku's liveblog coverage of E3, folks! It can make you rich, if you register domain names as soon as the products are announced.
Fusible notes that the owner of wiiu.com is hidden behind Whois privacy and currently is a Shopping.com affiliate site that displays videogame and console ads.
wiiu.com! What you need, when you need it.