WordPress MU

Hi,
I am runnign WPMU and trying to stop spam comments on my users' blog. After searching the forum, these were what I did:
1. Download and upload the Akismet plugin file akismet.php into /mu-plugins directory.
2. Login as admin. On the Dashboard page, it asked me to enter API key to activate the plugin.
3. Since I have had an account at wordpress.com, I found the API key.
4. Enter this key value through the MU admin Dashboard. It seems to work to the admin account.
5. I thought it should take care of all the users' blogs.
6. But when a user logins to his blog site, he gets the same message asking for the key. It means this user has to register wordpress.com to get a key.
7. Is this the way supposing to work? Or there should be way to control from admin site?

Thanks

For using Akismet in wordpress mu, you need open the file with editor. find this line enter your api code:

// If you hardcode a WP.com API key here, all key config screens will be hidden
$wpcom_api_key = '';

Do note though that per Akismet's lisencing, your users are supposed to get their own key. Your single key is not for a sitewide installation like WPMu unless you have an Enterprise lisence for Akismet.

If Akismet catches you, they will invalidate your key.