It has been requested that people leave an email address on their Blogger profile. This can be useful if you want to contact a commenter directly by email, rather than leave a comment on their blog.
On AOL Journals, an email address was provided automatically, as that was included in the screenname, which in turn was included in the URL.
There is one caution associated with this: leaving an email on a profile exposes you to the risk of spam. You may wish to set up an email specifically for the above purpose, and change it when it becomes clogged with junkmail.