All data relating to a merchant’s customers that a partner collects on behalf of the merchant (excluding any sensitive personal information) must be sent back to Shopify.
I’d like some clarification on this as well. We are a platform that enables merchants to chat with their customers online, through email and social channels. This means that any email the merchant receives at their email channel or through those channels, appear on our platform. In those conversations, we collect the other party’s name and email address, and the contacts which exist on our platform for a merchant might or might not be relevant to Shopify (could be that the merchant is in an email conversation with another app provider), so it doesn’t seem to make a lot of sense to sync the data back to Shopify. In fact there’s no real way of determining whether a contact is relevant to Shopify as a Customer resource or not.
The other issue is that if multiple apps collect name + email + phone, and with each app syncing their own version of the data back to Shopify, wouldn’t that conflict (last write wins) and possibly mess up the customer information on the Shopify side? Wouldn’t this also result in a large number of Shopify Customer objects being created on the merchant’s store, regardless if the customer was actually a customer or purchased anything?