There's no doubt that most will fail, but not because their idea is bad. They'll fail because they can't execute or, more important, form the right partnerships. In that sense, the format of Demo, at least right now for this crop of startups, isn't all that useful. Far more important is their executive team and even their VC sponsors.
As was the case last January, there were a few excessively bubbly founders who should have let someone else pitch their idea, but for the most part this bunch was more polished and practices in their delivery. So much so, that you can bet that if they didn't mention their business model, they don't have much of one.