I was looking into activities to do in Seoul and I saw a free public government sponsored bike rental. To use the rental, I need to give them some sort of ID for the duration of the rental. The ID can be a Student ID, Alien Registration Card or Passport. In this case, since I'm a foreigner, I have to use my passport. (I assume the student ID is for Korean Students.) Even though I understand their reason for asking me to hand over my passport as identification, I feel uneasy doing so.
As a general traveling question: Are there other ways to protect yourself from being asked for your passport for tourist activities other than the guidelines below?
Check out the location online (if applicable) and online reviews to determine legitimacy
Make copies of your passport and store them somewhere safe
Use common sense.
I'm not expecting a "hard" answer to this question but insight to the problem would help.