Native social media ads -- the ones that appear right in your Twitter and Facebook streams -- exploded in 2013. Love 'em or hate 'em, they're only getting bigger in 2014. This year, expect some significant, if slightly creepy, advances in location-specific targeting. Twitter, for instance, just unveiled a feature enabling paid Tweets to be targeted by zip code. You walk into a neighborhood, for instance, and suddenly Promoted Tweets for the local watering hole, dry cleaner, and McDonald's (MCD) pop up in your Twitter stream. This kind of "geo-fencing," which Facebook has had since 2011, enables businesses to court nearby customers who might actually want to get ads offering special deals, in-store specials, etc. The upside: more relevant ads and promos you can actually use. The downside: more ads.