You can directly trade control with participation. If you want to increase someone’s participation, give them more control.
If I wanted you to participate more in this blog, I’d give you an authors account, or let you moderate the comments, perhaps put you in charge of promoting content.
If you have an official Facebook group, appoint some officials from the community to help run it. If you have a blog, let people from your community contribute. If you have a Flickr profile, create a Flickr group and let others control it.
Just how little control are you comfortable with?