last year, i had like 8000 members, 2000 twitter followers, 2000 on facebook page, still can't motivate the members to be active on the site.
it's a competition type of sites, you pay 2$ you enter the competition, we tried free, members were still signing up but not submitting content. We changed the design and now we support mobile devices, still nothing. To the point where investors got angry.
I have huge number of users in my database, big number of twitter followers, but i guess this is what happens:
I sign up, I see that no one (or very few people) have contributed, i become afraid of being spammed, i leave. Lets take SE network as an example, more people come because they see other people around so they know it's very active, and that's how beta sites get bigger.
I was thinking of creating fake accounts and submit contents just to let users see some activity on the site, not sure if that's the best way to do it.
So how do start ups that rely on the user generated content encourage the users to start using the site?
You need to provide value to your users.
From your description, I don't understand what your site does but clearly it doesn't provide enough value for people to participate.
If a user really has to pay $2 and then "generate content" then I'm not surprised no one is doing that.
In general, in websites where users contribute content, the vast majority is readers and only few produce content, which means you need a lot of users in total to get some that contribute.
There's nothing terribly wrong in creating sock puppet accounts early to jump start the community, but what is much more likely is that you mis-attribute the cause of your problems to "users being afraid to be spammed".
Again, I don't know what your website does but must likely explanation for why users don't create "content" is: doing so doesn't provide value to them.
I've been researching what it takes to build online communities since the pre-web days (grad school RPI, started in '93). I cite my time online because it factors into my answer:
Online activity is a dynamic ecosystem that changes over time, in terms of media mix/ratio, in terms of the locus of activity, and in terms of whether the "center" can hold.
Part of your problem is you can lead a horse to water. There are tricks, as others have suggested, game theory, rewards, Skinner boxes. But they don't address the core issue.
It's like a town square. If you have real estate on the town square, and the center of town dies in favor of the mall on the edge of town, you're screwed, no matter how many flier sales you offer.
The town square of the Internet has shifted many times over those years. listservs, BBS's, IRC, Usenet-- they all directed users to a central area to meet and communicate. The Web, with contextual comment boards and user generated content, was a great diffuser. Distributive systems can be very powerful, as we've seen with the move from mainframes to PCs, from wonky code to very accessible HTML. I like distributed systems.
But the diffusion into a gazillion town squares on the web fragmented audiences, terribly. People congregate, but they had to have strong reasons to arrive and congregate, and then, to participate, and contribute (slashdot et.al). Audiences became more isolated with the birth of the Web. It's a lot like how TV/hearths took people off their front porches and isolated them from the neighbors in their living rooms. How automatic washing machines in homes destroyed communities of women who had traditionally gathered on wash day.
From those diffused spaces, town squares are starting to re-emerge. "Congregations" of sorts are defragmenting a bit. Call it the "Facebook Effect."
I'm not a fan of walled gardens, ever, but if you are playing kickball on one playground (to mix my metaphors thoroughly) and the hot kickball game has moved on to a different playground, staying put isn't going to do you much good. And you could offer free balloons or hot dogs to draw people to your kickball game on your playground, but at some point, the hot game is going to move because these things do move around, as surely as Friendster begat tribe.net which begat FOAF which begat MySpace which begat Facebook.
Or how RadioUserland and RSS begat Movable Type and Blogger which begat LiveJournal and Typepad which begat Wordpress and Tumblr, which begat... Medium?
I'm here on StackExchange for the same reason. This is an interesting playground. How's the kickball game here?
You need to qualify your members. Thousands of members doesn't mean anything if they're not the right members. Define the type of person who creates the content you want submitted to your site, and make sure that's the type of person you're actually getting to sign up. If they're not submitting content either:
I'd bet you have an audience mismatch. You may have built an audience of people interested in seeing these competitions, but not one that actually participates in them. Does your audience have the tools needed to create the content? Do they have a need to participate in competitions, or get the prize the competition offers?
In any case, it sounds like you've been making improvements based on what you're guessing users want. Take the guesswork out of it. Do more customer development; ask "why" multiple times to make sure you're getting to root reasons of feedback.
There are several posibilities how acheive this:
There are dozens of ways. Don't limit your imagination! Just pay attention that users don't start posting "crap" just to "post something" (this is the biggest problem just after the yours - 1) inactive users, 2) active users providing inappropriate content)