Modchips for the Nintendo Wii appeared just a couple months after the console's availability, opening up the black market for the piracy of Wii games. Following the release of the modchips, the demand of the Wii soared in places such as China, since pirated Wii games could be purchased on the black market for approximately $1.30.
Nintendo is finally putting some effort into thwarting the viability of Wii mods, as reports from Japan indicate that the latest console hardware revisions are now much more difficult to modify with current chips. Three pins used by current modchips to alter the console's drive software are reportedly now physically cut, making modifications impossible for all but those with highly advanced skills and tools. The hardware revision has only been discovered in Wiis from Japan, though it's reasonable to expect that anti-mod measures will soon make their way worldwide.
News source: DailyTech