StumbleUpon – a content discovery engine – announced a complete rebranding of its platform last December in an effort to make the site more visual and easier to use. Now the company appears to be focused on keeping visitors on its site.

The newest update removes all direct links, meaning any time you stumble, you have to stay on StumbleUpon. Previously, if you were logged in, you could “X” out of any page and go directly to the original site. Now StumbleUpon forces users to remain inside its iframed version of the site.

If you want to go to the direct link, you have to copy and paste the link and delete the StumbleUpon portion of the URL. It appears that logged out visitors can still close the page by clicking on the “X.”

The decision to keep visitors inside will negatively impact sites that rely on StumbleUpon for referral traffic or SEO boosts. A similar decision was made at Digg, which resulted in backlash from its user base. Early comments suggest that StumbleUpon’s users aren’t too happy either.

[Image credit: Alan Levine]