Yes you can get anyone's email ID who is on Orkut. This is a serious security hole and violates many privacy statements. You can actually get anyone's email ID on orkut.
- Goto the persons orkut Profile page.
- Click the ignore user link.
- Sign into Google Talk using the google talk client provided by google
- Click on Settings near the top of the main google talk window.
- On the list click Blocked
- And there you will have the person's email ID
I hope orkut fixes this soon. Otherwise many email ids are going to be compromised.