MG Siegler is discussing Tumblr here, but he hits on a maxim that should be applied across every social media platform, promotion, and campaign: Different users need options for different intensities of interaction.
If the only way for someone to enter your contest is to write a multi-paragraph entry accompanied by a photo, you’re missing out on a large number of users that would be happy to participate if the barrier to entry was lower.
Instead, what if you gave prizes to those that voted on their favorite entries and helped select a grand prize winner? Or what if you allowed users to comment on other entries, and then gave one prize each day to the best, most original, or funniest comment?
It takes additional planning to get right, but the opportunity to engage users that would otherwise not participate is too important to pass up.