If you write a scrap with a URL in it, Orkut requires you to complete the image verification (CAPTCHA), however if you post any URL within the Google network you are not required to do so, this flaw can be used to post url's bypassing the image verification.

http://upload.video.google.com/searchhistory/url?url=//YOUR_URL_HERE
EXAMPLE: http://upload.video.google.com/searchhistory/url?url=//www.megaleecher.net

The flaw is being successfully exploited by spammers and Orkut virus makers for mass scrapping users with live links bypassing the whole SPAM protection mechanism of image verification.