Make 20 different user accounts. Create 20 different pieces of content, from 20 different people. Rinse and repeat. To a new user, it'll look like there's some

Make 20 different user accounts. Create 20 different pieces of content, from 20 different people. Rinse and repeat. To a new user, it'll look like there's some serious activity, and they'll join in. I believe this is what Quora did.