The only problem you might get, is if you have two users withe the name "jones", both would try to get the username "jones". Then the controlpanel denys the second one with an error message like "username jones already exists". This might confuse your customers because they cant see the user jones in the users list, when it belongs to another customer
Point taken till. But I don't think that applies to me as I don't have clients. Only friends and family, so I have full control on who I want to register and what names I want to give them.
Others might take heed to your posts though. As for myself, I just want to make this as least painfull to my computer illiterate parents and friends.