In the last two weeks I have had hundreds of Chinese Customers sign up all with variants of firstname.lastname@example.org email addresses. They haven't bought anything so I'm guessing they are just probing but I cannot anticipate what is about to happen.
Yep, I see this often. They're automated spam bots. Most likely they'll subsequently use the registered accounts to try to hammer the share wishlist and/or send-to-friend functionality. Both of these features are massive spam-bot magnets in Magento 1.x and should be either disabled entirely or put behind robust CAPTCHA solutions.
Also, put a CAPTCHA (e.g. reCAPTCHA) on the customer registration as this will prevent these fairly basic spam-bots from registering in the first place.