Brands are relying too heavily on "going viral" and "amplification through social networks" and "sharing". As a result there are far too many social media promotions happening at the moment producing less than average ROIs. Big budget promotions are only receiving very little uptake.
It's pretty much the reason I recently won a car. In fact right now I am in with a pretty good chance to win $10,000 in a video competition... where less than 30 people entered.
Brands fail to understand that to run a big social media promotion you either need a cracking idea, a big media buy, or an already established audience. You can't launch and expect big results from your small community.
Instead, start with small, regular promotions until you've built up a sizeable audience. Then start giving away cars and large sums of cold, hard cash.