I don't understand the issue, from the banks perspective those are basically your username. It's not like they need to trick you into giving them a number they issued you. EDIT: The only problem I can think of is that it may encourage users to be loose with their info, and therefore be more susceptible to phishing attacks.
I'm sure some customers would consider themselves sophisticated enough to "know" this is a "real" Citi page, but if they were actually sophisticated they wouldn't touch this with a ten-foot pole.