Publishers are testing boundaries in mobile native ad delivery, fearful of crossing the line with their users and mindful of the difference a small screen makes, Lauren Johnson writes. Advertisers are lining up for Facebook's and Twitter's audiences, but the ads are intrusive. Sponsored content is harder to spot on a tiny screen, but mobile offers a few viable alternatives. "Our content with native ads almost works better on mobile because of the native aspect," BuzzFeed's Jonathan Perelman says. Strategy Analytics' Nitesh Patel, adds, "Those boundaries will be tested over the next 12 months in terms of publishers and what works for them. The challenge of a publisher is to put the content out there and make sure that it's done in a way that does not irritate the consumer experience."