-prints, photobooks, physical stuff like that. people into making their photos look vintagey would surely love to place their fake polaroid next to their record collection.
-All instagram images are geotagged and timestamped. How about you partner with media outlets and allow them to leverage all the images being taken for specific events? "instagram @ SXSW" or whatever.
-"license this image" - Lets say I run a food blog. clearly a great place to look for imagery of food is on instagram. I could affordably license the image and give money to the photographer (and instagram gets a cut.)
-etc, etc, etc,
These are just off the top of my head. I'm not saying these are brilliant ideas, or that they would necessarily work at all. What I am saying is that I wish that we'd explore solutions outside of "lets plaster ads all over it." It's an ineffective way of making money that's just stolen from the slowly-dying magazine industry, and is that really the industry you want to emulate?
It would also encourage brands to put good content up, rather than just being a boring corporate mouthpiece, which is always a plus.