Here is an example of a site that already utilizes email addresses to login, that is vBulletin software: http://forums.electronicarts.co.uk/
In my opinion, it should be a default option for the admin to choose whether to use a regular username or email address to sign in. I would automatically choose email address login for my site.
The person trying to log into your account had the following IP address: 203.153.29.50
The person trying to log into your account had the following IP address: 190.202.184.75