Like because: Design, interface, potential for information gathered there, potential use. You know all this.
Scared because: You're creating an information portal when Google does a better job. You need a massive amount of users to give you all this information when there is really no incentive for them to do so. Say I am in Amsterdam and want to go to a club. I go to google and type in "Amsterdam club". I will then get lots of information, reviews, photos, etc from a wide variety of sites. The very first entry is a map of a bunch of clubs linked to reviews. Fantastic! It's open, accessing every site in the world, and filled with info that is relevant to me. Your other problem that I foresee is accuracy of data. Clubs/restaurants/hostels close/renovate/change owners all the time. You need your listings to be curated and current. As soon as you fail once you lose that user.
I haven't backpacked in over a decade (1998) and when I did I relied on Lonely Planet books to get me places and then locals to steer me towards the good stuff. You get nothing more current, fresh, and accurate than locals, local zines, and lamp post billings. As for hostels there are many, many, many sites now that have traction and offer me more value (again, I just googled it). Trip journal sites abound (and offer many revenue possibilites like book journal printing). Restarant review sites abound, as well. User generated travel content sites have to be one of the toughest markets to crack. And with all the niches you're trying to combine into a walled garden I just don't see a clear path to success.
To add... as someone said, people just don't travel all the time. I used to be a member of a travel blogging site about 6-10 years ago. Haven't been back to it since and completely forget what its name is/was. It was a big one and very popular. Google replaced it for me.