I have attended a few StartupWeekend events and it is always exhilarating to participate in them. All the energy and enthusiasm is contagious to say the least.
One pattern I have noticed so far is that a majority of the projects just fizzle off, after the weekend. One of the main reasons is the fact that the team realizes that the idea is either not feasible or does not make sound business.
In reality, VCs always look for 'the team'. If you have an A-team, come what may, they will execute. If halfway through the endeavor, they discover that the idea doesn't hold water, they will come up with another one which will. Remember, they are the A-team.
The biggest problem at StartupWeekends is that there isn't enough time to iterate, and come up with fresh ideas. You present an idea on Friday, and have two days to execute. If the Product Manager determines that the idea doesn't make business sense, it is too late to turn the ship. The developers are already half way through the project and are not going to stop. Even if you stop, and change course, the chances of having a demoable application by Sunday evening is pretty slim. So, in order to save face, the team moves along and completes the implementation (demo app).
After the weekend, the idea fizzles off since the momentum is lost and no value is seen in continuing the idea. In cases where there is a lot of synergy and great teams are formed, they continue to meet and hash out ideas that they finally implement.
So, the key to a successful StartupWeekend is not the idea, per se, but the team you form. Next time, pick people who complement you and make a great team and success will follow.