Some Orkut users are getting an error when they try to send friend requests. This error message says Adding friends Service is temporarily Disabled. This problem can occur when you try to send too many friend requests in a short duration of time. Once you are blocked, you will have to wait for about one week before you can send new friend requests.
When I checked Orkut help regarding this topic, I came to know that Orkut had set a limit to curb spam and viruses.