Funny, I first noticed how they don't eat their own dogfood. They don't have a captcha on their contact form: http://www.solvemedia.com/contact.html. Seems to me like that would be a good place to have one.
Vidoop was bought up by Confident Technologies, which is still doing the image-based captcha as well as image-based authentication for Web and mobile: www.ConfidentTechnologies.com. The free MyVidoop service is still around too.