While most people know better than to touch electrical components with their bare hands -- especially when plugged in -- Nokia (and no doubt many others) sees the defect as a safety risk and want all the units returned for replacement.
Unlike many recall processes, this one apparently started at Nokia's behest, upon discovering the issue during internal testing. That's much better than being taken to court before issuing a recall, since at least now Nokia has ground to stand on saying they were being proactive. If you own a defective charger, Nokia is replacing the units for free.
Nokia hasn't released information on exactly how many chargers are affected, but it's potentially upward of 14 million -- though, that figure could be inflated. A third party manufactures the part, and Nokia may not have figured out just how many are in the field. Even if the number was that high, it would still pale in comparison to the battery recall a few years ago. That particular issue set them back a substantial amount.
To handle any recall requests, Nokia has set up a website intended specifically to help people identify the chargers and get a return going. If this recall should pan out anything like their previous one, Nokia will likely try to go after the manufacturer, BYD Electronic.