My site seems to be getting traction but still users dont post in it I am still doing it after 4.5 months online

My portal is starting to show some traction. We've been online 4.5 months after 1 year of developing it. We already have close to 50k twitter followers, 1,000 visitors a day between PPC + Organic, 7 - 10 daily chats with the vet, close to 3.5k in Facebook. Our bounce rate is looking good below 40% and below 35% for Mexico which is our core market. Alexa ranking is looking good already below 400k. The thing is still users are not posting anything in the forums or classifieds we still have to do it everyday to keep the site on the right track, I am wondering if this is normal behavior until we really build a solid community. What are your thoughts?

Also I am wondering what are your thoughts on using your daily marketing budget only in FB to grow faster our FB user base and stop PPC or would you continue doing a combination of both?

So you're trying to build a community? That's good, but you have to remember that you can't create the community. The community creates itself. All you can do is provide tools, content, and value.

If your model hinges on the community being the value for the community, you're running backwards on an escalator.

Here is my advice:

1. Provide extremely valuable content (Looks like you may already be doing this to an extent)
2. Refine and improve that content to match what's trending on your website. People are inevitably visiting certain content more than other content.
3. Interact with the people who visit your site. Invite interaction. You're already doing that with the chat client. Awesome, you need to build on that.
4. Interact with your users externally. Yes, your users are going elsewhere to have the conversations you want on your site. You have to go where they go. Go post comments on other websites and answer questions in other spaces. Don't post links to your site, however. They'll follow the bread crumb trail if they really liked your advice/interaction.
5. Lastly, be patient. The community will build itself if you focus on helping people, delivering value, and giving a shit. People want you to care about them, that's it. Focus on that, above all things.

Good luck Daniel.

I would add to Ryans list, run some competitions and provide some other styles of encoragement for them to start the ball rolling, it is likely that everyone looks there, sees there is nothing and so doesn't bother going any further.

You need the initial population of those areas of the site in order to "be the one who goes first".

You don't need it to be cash prizes it can be prizes like extra hours consulting or the landing page listing for their business for 2 weeks ... or something like that.