@ned, cofounder of steemit talked about adding advertisers in the future.

Imagine a restaurant buys steem power and starts a steemit account. A steemit user eats in the restaurant and posts a review of the experience. The restaurant upvotes the positive review left by the customer effectively giving the customer a SBD rebate for the good review.

Also, he talked about a small add at the bottom of posts, relevant to the content and optional for the author. The advertiser buys steem which is transfered to the author for each view and click through.