signup with only email adress?

Is it possible someway that my customers only need to signup with their email adress instead of both username and email? For after that to be directly redirected to the payment site ?

Hi Thomas,

WordPress requires a unique username for each user, in addition to a unique email address. However, it is possible to create a hack that automatically generates a username in the background and then hides the username field from the user during the registration process. This gives the effect of not requiring a username. You can then use a plugin like WP Email Login to allow your users to login with their email address instead of their username (which they won’t even know they have).

For more information about this hack, please see this thread.