Ad formats. LinkedIn says, "Text or text and small image ads can be purchased via the API. These are different from display advertising, which is a product available through our Marketing Solutions efforts." Facebook by contrast allows API access for its standard right sidebar ads, which are the workhorse of its ad system. (See AdExchanger's rundown of all Facebook ad formats.)
Partners. Facebook has awarded 51 Ads API badges, and more companies than that are leveraging its Ads APIs. LinkedIn has three: Unified, Adobe, Bizo. Will it grow? Almost certainly, but consider that Facebook started its API program with API partners in at least the teens. LinkedIn is clearly taking it slow.
LinkedIn tells us: "Right now, it’s a premier program, where we evaluate and accept partners who are the right fit. Our product and technology teams work closely with potential partners to review, test and approve before we launch our partner's offering."
Enterprise Skew. These three partners are telling choices as they're all geared toward the enterprise-class marketing decision maker. Adobe is the only Facebook PMD to hold all four of its badges (Apps, Insights, Ads, Pages). Its selection by LinkedIn further extends its status as a comprehensive "engagement" platform in social, mostly for Fortune 500s. Unified is positioning itself as an enterprise-class marketing "operating system for social." Bizo is arguably the B2B digital ad platform of record. It is likely to bring in a somewhat smaller size customer. LinkedIn will no doubt be closely watching the relative value it can deliver relative to the other two.