The email address used by the blog owner is at the choice of the blog owner. The email address used by you is at your choice. You have the final say here, and this detail isn't always obvious to everybody.
There are several interesting side effects, some which used to provide opportunity for abuse.
- You can accept membership using a different Google accounts.
- You can forward (as email) the invitation to your friends, and one of them can accept membership, using your invitation.
- If you accept a blog membership invitation in the Inbox of one email account, but use a different email address to authenticate yourself to Google, note that the latter email address becomes the Google account, for your blog membership. The email address that was used to send the invitation is irrelevant.
- If you are currently logged in to Blogger, you will by default be using that account to accept the invitation. If you are transferring control of the blog to a different (maybe new) Blogger account, select "Use a different account" instead of simply using the account displayed. This detail is one reason why we highly recommend that you use 2 browsers or computers, or repeatedly clear cache and cookies, when you transfer control of a blog from one account to another.
Once again, we see that if you are inviting your friends to be Authors of your blog, you must be able to trust your friends. The Blogger Permissions wizard can't verify what Google accounts become Authors, because the account used to authenticate membership is the choice of the new member.