This is natural when you abide by "release early and iterate." Most of the companies 11 weeks old. When you release, you haven't yet implemented your entire vision. That takes much more time to develop internally and become obvious to outsiders. But the founders know that the first release is just the tip of the iceberg.
There is pretty much not a single startup in this session that isn't directly attacking a large market or has plans to expand into a market orders of magnitude larger.
There isn't any video. If you're curious about one in particular, contact them. They're all stand up folks.
"Google began in January 1996 as a research project by Larry Page, a Ph.D. student at Stanford.[1] In search for a dissertation theme, Page decided to explore the mathematical properties of the World Wide Web, understanding its link structure as a huge graph.[2] His supervisor Terry Winograd agreed and Page focused on the problem of finding out which web pages link to a given page, considering the number and nature of such backlinks to be valuable information about that page (with the role of citations in academic publishing in mind).[2] In his research project, nicknamed "BackRub", he was soon joined by Sergey Brin, a fellow Stanford Ph.D. student and close friend, whom he had first met in the summer of 1995 in a group of potential new students which Brin had volunteered to show around the campus.[2]"
It depends on how you define a hacker project. That is a fair characterization if you say that a hacker project is something that doesn't come out of a normal business process, regardless of the corporate structure that surrounds the people hacking away on it.
"... is there any video of the presentations? ..."
Asked of previous demo days, and the standard answer has been "no" - probably due to companies not yet ready for release. I thought the purpose of demo day was to allow VC's a sneek look at the latest YC recruits not a general public launch.