1. Obviously allow password resets to on file email addresses.
2. If the above fails, try geocoding the address with google or geocode.us. If it successfully geocodes, ask the user for the address used to signup for the account, and tell them the zipcode the address was in so they know what address if they moved. Take the address they give you and geocode that. If they are very very close in lat-lon it is the same address (you might call this a geo-hash of the address).
3. No email and fake address? Well, this is a consequence of lying when they signed up, so you might say TFB and let them start a new account.
I can't give you more alternatives without knowing what other info you have on them, but the first two here should cover 90% of your users who didn't lie about their address based on the statistics that I pulled from my butt.
1. Obviously allow password resets to on file email addresses.
2. If the above fails, try geocoding the address with google or geocode.us. If it successfully geocodes, ask the user for the address used to signup for the account, and tell them the zipcode the address was in so they know what address if they moved. Take the address they give you and geocode that. If they are very very close in lat-lon it is the same address (you might call this a geo-hash of the address).
3. No email and fake address? Well, this is a consequence of lying when they signed up, so you might say TFB and let them start a new account.
I can't give you more alternatives without knowing what other info you have on them, but the first two here should cover 90% of your users who didn't lie about their address based on the statistics that I pulled from my butt.