(AP) -- Poor Instagram users. First, their beloved photo-sharing application moves from iPhone-only exclusivity to the Android phone masses. A week later, Facebook swallows up the tiny startup behind the app for $1 billion. The purchase sparked worries that Facebook might shutter Instagram or change it for the worse by harvesting their personal information or shoving ads into their carefully curated photo streams.
"I've tried very hard not to be part of the Facebook ecosystem," says Darwin Poblete, a Brooklyn, New York-based architect who has used Instagram since its early days. "Now I feel like the purchase has sucked me in. I'll have to see how the privacy settings change to decide if I will leave it."
Instagram has attracted more than 31 million users in less than two years. Its near-cult-like early followers were loyal iPhone users who flocked to the app for its ease-of-use, its playful filters that can make even boring photos look artistic, and its lack of ads, status updates and other clutter. Apple named Instagram the iPhone App of the Year in 2011.
To be fair, both Facebook CEO Mark Zuckerberg and Instagram CEO Kevin Systorm sought to reassure people that the app is here to stay. Unlike all the other startups Facebook has bought, Instagram will remain available to people who don't use Facebook or don't want to connect it to their accounts on the world's most populous online social network, the CEOs said.
"Millions of people around the world love the Instagram app and the brand associated with it, and our goal is to help spread this app and brand to even more people," Zuckerberg wrote on his Facebook page announcing the purchase on Monday.
It's hard to say, though, what Facebook might do a year or two from now. After all, its site's constant evolution has been a big reason for its success. Doing things the old way just because a few users complain isn't the Facebook way.
For Samantha Hutmacher, change isn't necessarily a bad thing. The college student, who uses both Facebook and -since last week- Instagram, says that if Facebook tweaks the app, "I assume it'll be more creative."
While a lot of people complain when Facebook makes changes to its site, Hutmacher says she "can't pinpoint any particular time" when she wished that her Facebook page didn't have the new features the company has added over the years.
"It kind of grows on you," says Hutmacher, who studies elementary school education at the University of Missouri in Columbia, Mo.
Instagram already feels a bit like Facebook, but with all the noise of status updates, links, ads, videos and games stripped away. That's part of its appeal, and a large part of why Facebook saw it as so much of a threat that it paid $1 billion to buy it.
"They are growing like mad on mobile, and Facebook's mobile platform (including its app) is mediocre at best," wrote tech blogger Om Malik on Tuesday on GigaOm. "Facebook is not a mobile-first company and they don't think from the mobile-first perspective. Facebook's internal ideology is that of a desktop-centric Internet company."
Instagram is a social network only for photos, but even those are different. Users seem to put more thought and caring into an Instagram photo than they do for a typical Facebook snapshot. These aren't your party group shots, tagged with the names of everyone there, nor are these the endlessly re-shared kitten photos with funny quotes attached to them. Instead, users are more likely to share, say, a photo of a cup of tea with a filter applied to it, so it looks like it was taken with a film camera 30 years ago. Children are popular subjects too, as are tulips and Easter eggs when they are in season.
Deb Johnson of Long Beach, Calif., likes to post photos of her dogs, two Rhodesian Ridgebacks. She also posts shots of food she eats, most recently a dish of Scottish salmon she had at a restaurant. To appreciate Instagram, she says, "you really have to appreciate the visual experience."
"Today I took a picture of something silly," says Johnson, who works in information technology, testing systems for insurance companies. Someone in her house had put a little Cookie Monster Pez dispenser inside a bigger Cookie Monster Pez dispenser, making a Pez dispenser-dispenser of sorts. So, Johnson snapped a photo. Instagram is so simple to use that these are the types of pictures that show up. In can take just three finger-taps to share an image on Instagram.
"There are hundreds of thousands of apps. Apps are not a matter of `build it and they will come," says Rebecca Lieb, an analyst with the Altimeter Group. "The price tag indicates that Instagram was not without other suitors."
In other words, Facebook didn't just buy any company.
"If someone could bottle their recipe for success, I guarantee they would. It's easy to use, works extremely well and adds an extra layer of functionality (with the filters)," Lieb says. "All of that combines to create the mojo that is the brand. Why isn't every soft drink Coca-Cola? Because it isn't."
Instagram's overnight success is reminiscent of another sleek, easy-to-use application that's gotten a lot of users quickly - Pinterest. Both companies tap into people's desire to share little life moments as they happen. And both give users a social network that is simpler and less noisy than Facebook.
"There are a lot of interesting social networks out there," says Gartner analyst Brian Blau. "And those are competitors to Facebook. One around photographs, (that's) one of the most popular things we do. It's a perfect complement to Facebook."
Facebook's challenge will be to keep loyal Instagram users happy even as the service expands to include many more people.
"We have seen this happen before when Facebook opened up its membership base from (college students) to everyone," Lieb says.
People grumbled at the time that this was the end of Facebook. It wasn't.
"People don't like change, but user behavior indicates that people will accept change," she says.
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