Despite the rapid success of mobile photography, thanks to great smartphone cameras and apps like Instagram, we’re still waiting for someone to finally figure out group photo sharing. Swirl, the latest app incubated by Betaworks in New York City, aims to solve that dilemma by relying on one of the simplest tools in social networks: hashtags.

Swirl’s free iPhone app, which officially launches today, taps into your Twitter and Instagram accounts to collect photos from your friends using the same hashtag (keywords designated by the hash symbol ‘#’). For example, in my feeds there are plenty of photos tagged #Sandy after the recent super storm that ravaged NYC. The app collects those photos into a #Sandy group, or Swirl, and also lets you favorite it to keep track.

“I was watching my friends use the same [photo] tags on a bunch of different networks, and I wanted a way to pull all that content together,” said Swirl founder Summer Bedard in an interview with VentureBeat. “People aren’t just tagging conferences, they’re tagging birthdays, weddings … daily things.”

Typically, when you use a hashtag on a social network, your post gets thrown together with all the other public posts using the same tag. You can also search for photos by hashtag manually on both Twitter and Instagram. By focusing specifically on hashtags made by your friends, Bedard says, Swirl can offer personalized and ultimately more meaningful, collections of photos. And since it happens automatically, you don’t have to go through the effort of searching individual social networks.

Some group photo-sharing apps have crashed and burned, like Color’s initial attempt at tying in location. Flock, another competitor, is also trying to bring together location and photos, but its technology doesn’t always categorize photos correctly. And it’s also yet another app that you have to download and convince your friends to use — something that holds back most group photo apps.

Swirl, on the other hand, collects photos your friends are already placing on social networks. You don’t have to convince them to learn an entirely new app. And since it’s relying on pre-existing data, Swirl has plenty of useful content to explore from the start. The app also lets you avoid spammy (or simply gross) photos, since they’re coming from your trusted friends.

“I want people to be able to access this data whenever they want and not have it lost in their individual timelines,” Bedard said. “I want them to feel a sense of connectedness.”

The company is working on adding Facebook access soon, but the big problem there is that Facebook users don’t use hashtags very much, Bedard said. Eventually, she also hopes to add the ability to follow collectors, or groups of people using the same tag. Swirl also organizes publicly available photos on its website.

Swirl is following in the path of other Betaworks incubated companies like Chartbeat and The NYC incubator also recently acquired the social news site Digg, and it’s aiming to revive the site after a prolonged period of neglect from its parent company.