One way of enticing people to join a community is to provide incentives. You may provide freebies or rewards in order to get them to sign up. This may be a good way of getting sign ups. However, if you want to entice action within your community, you this may not always be the solution.
The problem with incentives is that the moment they've received what they signed up for, they're through participating. It is better to target people who sign up because they're the type of people who enjoy participating in such community. The mentality of people who sign up because of these goes something like this. "No incentive - no action." If you're resources are limited and you don't have an unlimited amount of freebies, it may be harder for you to entice these people to take some action.
In order to remedy the situation where your list is filled up with dead leads, it is better to start at the very source - the sign ups.
This is where the challenge comes in. Instead of enticing people with rewards to sign in, you need to persuade potential members that they are the sort of people that would join your community. It may be harder to do this. However, once you've persuaded the right people, it will be more effective compared to enticing action from the "rewards only" people.
In order to salvage what you can out of the sign ups you got from freebies, look for ways to entice them. It may not be as promising as a 100 percent conversion, but at least you've tried something to take them out of the dead end list.
A community that has no activity is a dead community. So make sure you persuade the right people to join your community.