I once went to get a new phone at Best Buy, and the employee needed my email address. I gave it to here (firstname@lastname.com) and she insisted that it was NOT my email address. She insisted that it MUST end in @gmail.com or @yahoo.com, something like that.
We frequently sign up for stuff online, and when we enter our email address it won't let us sign up... we figured it is because the email address is too similar to our actual name, the name we've entered in the 'first name' and 'last name' fields (it happens to both me and my wife at least 2-3 times a year).