WALL STREET JOURNAL — Facebook Inc. is trying to rev up its advertising business with a little help from your friends. The social-networking site is aggressively pitching to big advertisers like Ford Motor Co. and PepsiCo Inc. the latest in a series of ad formats that tell users which of their Facebook friends have expressed interest in the brand or product featured in the ad. The so-called social-context ads, which Facebook started rolling out over a year ago, are based on data it collects on the likes and friends of its users. The ads appear on the right side of a user's homepage, with an image and headline from the advertiser...