It's practically de rigueur these days for web sites with a lot of users and data to have web services. For example, YouTube.com has a set of REST web services that returns essentially the public-facing video data that users have made available on the site. A harder problem, though, is how to get at the private data of those web site users using web services. On YouTube.com, users can mark their videos as private so that the videos are never publicly displayed and won't surface via YouTube's web services. Yet, there might be a reason that users would want a third-party developer to access their private videos via a web service. The third-party developer might offer a video backup service, backing up the videos onto DVDs and then mailing the DVDs to the user. Another possibility is that the user has a personal blog and would rather that his private videos only surface on his blog.
