Selecting Blog name other than username

Hello, I am planning to install Wordoress 3.0.1 ms . I am setting it as multisite. I would like to enable something similar to wordpress.com website.

In wordpress.com, while a user registers, it asks the user, whether they need a blog or not? I would like to use that function in my website. Is it possible?

Similarly, a user gets a blog with his username as the blog id. I wish to enable a field in registration where a user needs to enter his desired username, and in the next field, he should enter his desired blog id.
Is this possible?