Unfortunately, usernames are very often reused, especially when a site simplifies matters and asks for your email address. This is an especially attractive bit

Unfortunately, usernames are very often reused, especially when a site simplifies matters and asks for your email address. This is an especially attractive bit of info because an email address and an easy-to-remember password can net you their email account (so you can delay discovery of your escapades) as well as every ecommerce site where they have an account. Gift cards for everyone.