On the surface the inclusion of Caller ID in CyanogenMod seems pretty nice. This is a feature that you would pay your carrier for, but things get a little fishy when you consider this service is being provided by TrueCaller whose business practices are suspect and even illegal in Europe. TrueCaller shares your personal contact information when you give it permission. This means that your friends and families contact information will be available for anyone who uses TrueCaller.
TrueCaller explains how they are legally able to collect your contact's information inside their terms of service.
By allowing Contact Information to be collected, You give Truecaller a right to use that Contact Information as a part of the Service and you guarantee that you have any and all permissions required to share such Contact Information with us. You may opt-out to prevent the sharing of Contact Information at any time.
According to TrueCaller it is your responsibility get the consent to share contact information from every person in your contacts list prior to using TrueCaller. TrueCaller claims to currently have 1.6 billion phone numbers in their data base. You can opt out of using TrueCaller, but you can't force others to opt out of sharing your information if you happen to be in their contacts list. Caller ID would be a great feature to have on CyanogenMod, but is it worth risking your privacy?
via XDA