I would appreciate if you could all share your insights on the following question:
What is the best practice for generating user ID (userID at something.com) and the ideal acceptable length of userID?
The user ID is generated for the consumer-level mobile device.
As a rule of thumb, I am setting to what is visible on the text field (15char max) and maybe 5 characters more to attach server generated "number" if the user ID already exists.
Users do not give any first name/last name before setting userID unlike Web service account creation.
So the current scheme is <user generated name> + number (5 digits max) if the ID already exist.
The service is in use for Europe.
Have you encountered any other scheme to create unique ID a part from attaching number at the end?