An app that helps people in San Francisco figure out what to do on weekends has developed a rabid following.

San Francisco Skyline

Sosh sends users details on about 500 different activities each weekend. Photo by Curtis Fry.

Sosh is the ultimate hipster app — it curates things that are new, fun, weird and memorable. If something gets bookmarked by too many people, it’s no longer pushed to other users. And for now, it’s only in San Francisco.

Sosh just closed $4 million in Series A funding led by Battery Ventures. But wait, venture-backed start-ups are supposed to be scalable, right?