Take this one with a pinch of salt by all means, but perhaps take it more seriously than you would a typical unsubstantiated rumour. Nintendo users over on Resetera have been complaining about suspicious account activity on their profiles, and enough people have joined in the conversation to suggest that something might be up.
These latest examples, which may or may not be linked to some sort of concerted scam or hack, follow on from a short statement shared on one of the company's support accounts on Twitter earlier this month, which warned of a rise in the number of enquiries related to account security.
The solution in both cases is simple: enable two-step verification. It's simple enough to do (you'll find instructions here) and even if these reports are nothing more than isolated incidents, it can't hurt to have tighter security on your account, especially if you've linked it to a bank/Paypal account.