We Heart It is all about what things, interests, causes or hobbies people want to be identified with. It's kind of like a visual ID, Shimmin added.
"Here you get rid of these contractual social obligations," said Shimmin. "This is more emotional, I think. It's more about following images than people."
We Heart It youthful base, and the fact it's adding a million new users a month, gives Pinterest something to worry about, said Patrick Moorhead, an analyst at Moor Insights & Strategy.
"I had not heard of the site, but my teenage girls had," he said. "Social media is like TV channels, in that as long as it is very different and has enough scale, it can pull users away from the largest sites. This is very different from Pinterest, which has drawn an older and more diverse crowd but 20 million active users is impressive."
Pinterest needs to figure out how it could draw in the 16 to 24-year-old demographic, Moorhead added.
Shimmin, however, said there's plenty of room for both Pinterest and We Heart It to succeed with their own user bases.
"The market for social network destination sites is phenomenally large and vibrant and able to support a wide array of audiences," said Shimmin. "I think Pinterest and We Heart It have a different philosophy about them and I think the market can house both. You don't' have to pledge your allegiance to one or the other."
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