Calling customers, "guests". A customer is someone with a business relationship with someone/something else. They're exchanging money for goods and services and have a right to expect certain value for their money.
A guest is something else entirely. A guest has no implicit right to expect a certain any particular level or quality of services. They are dependent on the magnamity of the "host".
Calling a customer a "guest" robs them of status.
You might want to think about it a bit more before putting it to work. The comment with the streams example is far, far better.