Phone numbers are easy to canonicalize: convert to international form.
Email addresses can be effectively canonicalized by lower casing. Not many mail servers are case sensitive these days. Additionally, for the local part, you can generally strip off anything after a "+", and with gmail, you can drop any period in the local part. (Granted, it's not perfect-- so make sure that's not a security concern.)
These techniques have been working fine so far in my app for my "Find My Friends" feature.
Email addresses can be effectively canonicalized by lower casing. Not many mail servers are case sensitive these days. Additionally, for the local part, you can generally strip off anything after a "+", and with gmail, you can drop any period in the local part. (Granted, it's not perfect-- so make sure that's not a security concern.)
These techniques have been working fine so far in my app for my "Find My Friends" feature.