This is a 2 step process to find the emai id of an Orkut User.

1. Go to the Orkut profile of the user you would like to find the email id of and click on “Ignore user” tab given on left side.

2. Open your Gtalk and click on settings link given on the top and click on blocked users. Now you would see the Email ID which was previously invisible to you.

ie. in short

Orkut profile>Ignore user>Gtalk settings>Blocked users>Email ID