There is still some harm. It is easy to cause information leakage, and you can also register a lot of software with your ID number. The ID number is a code of the ID card itself, which can reflect the information such as the birthplace and date of birth of residents. Leaking the number won't have a bad effect. Now, some specific things, such as bank account opening, voter registration, business license and hotel check-in, all need ID cards. If you show your ID card, you will be registered and your number will be leaked, but it will not endanger our lives.