Over the past several months, there has been a quiet but repetitive topic taking place in the Google forums. A recent one was started by loupiote, who said "a couple of weeks ago, I have demoted the link yet, if i search "loupiote.com".
A more robust thread is at Google Webmaster Help where Google's John Mueller explains why Google may not be listening to your Google Sitelinks demotions and what you can do to help reinforce those demotions.
First off, he explains that Sitelinks demotions are not removals so despite you demoting them, they are not removed and may show up. It may also take time but if you are not happy, here is what you can do to help it along.
- use the "nosnippet" robots meta tag
- use an image (as others have suggested)
- use a robotted iframe
The content in that area should not show as sitelinks.
Forum discussion at Google Webmaster Help.