1. Strange, just tried the link and it worked for me - http://www.jivesoftware.com/resources/videos/clearstep/clearstep-overview.mov - so maybe there was some sort of hiccup in the system. Maybe try again and let me know if it doesn't work.
2. On intro videos the type of community does make a bit of a difference, i.e. B2B vs. B2C external community vs. internal team. I'm assuming since you posted your question here you're thinking about an external facing community. From my experience (I'm the Jive product marketing person focused on external facing communities and a community manager for Clearstep) I can't think of a B2C type of community that has done much if anything on the intro video front beyond a teaser type of video. For B2B communities I've seen a number of takes with many focusing on explaining the main ways to contribute. Below is an example email that Canadian Airports Council used. They had a monthly "tips" type of email approach but you can see how the content itself could easily translate to an intro video.