How to solve the chicken-egg problem when launching user-generated content site?

I'd suggest that you have to start by building some content first, before you have users. 

Start by identifying verticals / general content areas where you think you are likely able to build content and / or where having expertise clearly sets people apart.  

• Invite top experts in their field to contribute to the initial body of content.  
• If they are people who are trying to / have made a name for themselves this can be a great way of them marketing themselves. 
• Establish initial content experts in each category. They'll have a claim to fame of having helped start that category. Give em credit. Profile them, their business.  
• Look at top bloggers.  e.g. there are 5-10 top VC bloggers.  Rather than asking them to do more work - answer this question for me - look through their blogs ask if you can use their content and work backwards from their blog (answer) to creating a question & the content.  You can do this across categories - top vcs, top mommy, top tech, top you name it. 
  

You have to start by building the content first, otherwise it's like opening a store with nothing on the shelves. Might look or sound interesting, but if you walk in and there is no or little assortment, you leave and don't come back and don't tell anyone.

The chicken-egg problem so mentioned fingers "critical mass" of social site. Critical mass is a term entrenched in physics, social science, marketing and organisational dynamics. In recency, it has gained energy as a buzz phrase in social media and site development.

In social media and site development, critical mass refers to a minimal level of attainment wherein number of users and value of content are enough to sustain momentum of activity streams that attract and enmesh new users, who in turn increase content and classically stimulate greater network density thereby inducing growth inertia.

The growth strategy for attainment of critical mass in social network site highlights the following:
1. Development of Workable Business Model that can checkmate vicissitudes of business environment.
2. Integrated Value Proposition Alignment to Solution Provisioning for filling the gap caused by weakness of key market leaders.
3. Structured Brand Diffusion
4. Across-the-Board Product Launching
5. Deployment of Adverts, PR & Press Release
6. Enhancing Site Connectivity through Mass Link Baiting, Cross-Network Blogging, Incentivised Social Bookmarking and Inter-Network Activity Announcement.
7. Procurement of Users who are Core Activity Enhancers (CAE) via Structured Site Relationship Development Programmes.
8. Development of Feasible User Engagement Model that contains Effective User Engagement Structure, Optimizable User to User Network Booster and Categorized User Incentive Scheme.
9. Deploying Staff-Induced Content Development to augment generic User-Generated Content Development. 
10. Establishment of User Advisory Board which comprises well-selected High Value-Adding Users for boosting Content Development with rapidity and focus.
 11. Accelerate Social Currency Growth by implementing appropriate strategic alignment of Image Development, Content Development and User Engagement in sync with Strategic Objectives of the Social Site.

Dr Elijah Ezendu
Twitter: Ezendu
Skype: elijahezendu
LinkedIn: http://ng.linkedin.com/in/elijahezendu