Viadeo, the social network for business, has added five applications built on Google's OpenSocial platform. These apps are Twitter, YouTube, PollDaddy, a doc sharer called Ayos iShare and Google Presentation.

iShare will allow users to upload any file up to 100 MB and post it for download on their account. The Twitter app will allow a user to post their Tweet automatically on their Viadeo page. The Google Presentation function will allow them to convert Powerpoint presentations to Google and share them.

Viadeo is down in the ranks. Compete.com gives LinkedIn over 14 million visitors a month compared to 157,000 for Xing and 96,000 for Viadeo. Certainly, the ability of users to branch out and back with these apps should make it more appealing.

The question remains, however, not which business-focused social networks have the most features, or the most users, but the most utility. In that respect, I fear they are neck and neck. After years on the service, and over a year on unemployment, all I got, even with an old supervisor firing me job ads via LinkedIn, was a quick phone interview that went nowhere. That's a guy with some experience, at some high-profile companies, actively searching, with friends on the look-out.

ReadWriteWeb has theorized before that part of the limitations of LinkedIn, in particular, is the fact that it's a walled system. If its API opened up, it would benefit the social web as a whole, perhaps. But would it help the job seeker? The hiring manager? The sales or biz dev person looking for contacts? I am not sure.

But one person's experience could be anomalous. So let me ask you, the ReadWriteWeb reader: What difference has your membership in a business-oriented social network like LinkedIn, Xing or Viadeo made in your career in the last year?