I've also seen similar language described on other websites' TOS; didn't Facebook have a debacle about this too at one point? It was explained then that it was necessary basically because distributing uploaded/shared photos to CDNs and the like might involve additional production and distribution the user didn't explicitly authorize. They might need to copy your photos to give to the CDN vendor and the license needs to be sublicensable so the CDN vendor can legally copy shared photos across their network.
On the other hand, though, the marketing purpose part just sounds downright shady.
I don't think Facebook's questionable language contains the "fully sublicensable" bit, which clearly implies they plan to sell anything created using a DS.
(And even just the "worldwide, royalty-free, irrevocable, perpetual, non-exclusive" bit is draconian. Facebook was under fire for adding "irrevocable."
On the other hand, though, the marketing purpose part just sounds downright shady.