I would post this video right smack on the home page. To the right of the signup/tour buttons and try to make it btwn 30-90 seconds. Maybe with a heading like... See it in Action. And to stay consistent with the high end feel of your site I would try to make the video high quality.

Yes. Email away - I love providing feedback. While I do think a yammer style service would be useful I would try to focus on one thing and really knock it out of the park. If you are making the choice to pivot your product towards a yammer/bookmarking combo product that is new tech this is a new hypothesis and should be part of your overall strategy. As opposed to adding bells and whistles.

In my office, we all have common links... email, time tracking, bug tracking, PM web app, etc. And having a centralized bookmarking network would be useful. Especially if I could publish a bookmark to say all the sales people and say - read this o sales people it's useful. But you would have to ask people in management (which I am not) for a more important opinion since they are ultimately the ones making this decision. Or aim this new product at the front line employees and move it up the chain verses down.