I definitely liked the presentation. I won't tell you my opinion about your business, though. The thing about the ebay business model is, that it acts as a market place (like Amazon), but actually is more a social network (for people who want to buy and sell stuff). Thus your main problem is the "empty disco effect". Nobody wants to join a disco, that is empty and so a disco stays empty. Only if a certain amount of people starts using your service, you will get others to join in. Some of your weapons of choice are viral marketing (like Dropbox: bribe them to invite their friends + have a great product at hand that they want to show off with), integrating into a big social network (like Farmville or in some way "Angry Birds") and buying + integrating niche networks that do already, what you want to do (no example at hand). Of course other ways are also possible. How do you want to tackle that social threshold?
I'm planning to launched a promotion for a free movie ticket if they invite 3 friends and upload a video of something they want to sell. What do you think about that?