(CNN) – I’m just as reactionary and just as outraged as the next Internet user when I learn that a service I’ve been using for free is going to start selling my information to market researchers or excerpting my posts and pictures for its clients’ advertisements or charging me good money to communicate with an online cohort that might have taken me years to build.

Such is the case with Instagram, a free photo-sharing app for smart phones. Millions of people have downloaded the free app and have been busy taking and sharing photos of themselves and their fascinations.

Instagram has risen to the level of a Twitter as far as the culture around it is concerned. It has spawned a new visual language, a new etiquette of sharing and an outpouring of creativity in the form of contests, collaborative art exhibits and personal expression.

Instagram got so popular so fast that Facebook took notice and purchased the company for a billion dollars – (yes, $1 billion) – to bolster its own smart phone presence shortly before its IPO.

The problem with being bought for a billion dollars is that eventually you have to start showing the kinds of returns expected for a billion dollar company. That means either charging users for the service or, as in the case of Instagram, selling the users’ data. Instagram plans to use the photos people upload in targeted ads – much as Facebook now uses our friends’ updates as the substance for advertisements called sponsored stories, as in: “John says: My Starbucks coffee tastes great today.”

So now, presumably, John’s picture of Starbucks will serve that same purpose – creating a contextual advertisement. Instead of simply uploading and distributing our photos, we are working for the man.

Well, what did we expect? Did we think Instagram was just a couple of self-funded slackers trying to make the world a more photographic place? Simple though it may be, Instagram is also a massive platform of servers and storage.

There are people working there, coding the software, designing the interface, and figuring out how anyone gets to look at anything whenever they want to. They need to eat.

In a tactic now familiar to Facebook users, Instagram founder Kevin Systrom issued a blog post backtracking significantly from the original announcement and assured users that the company has no plans to use their photos in ads. But the damage has been done, and the Instagram community is on notice that they may not own the rights to the photos they upload.

If they had charged for the service from the get-go, Instagram would have likely had many fewer takers. Photo services from Yahoo’s Flickr to Google’s Picasa already existed. So instead of charging for their service, Instagram decided to get the biggest base of users it could, use its massive membership as leverage to sell itself, and then let the buyer (in this case Facebook) figure out how to make money. In essence, Instagram sold its users to Facebook. We were never the customers, we were the product.

So now that Facebook intends to cash in on its investment, it’s a bit disingenuous for those of us using the free service to cry foul. We may be entitled to free Internet (though that’s a topic for another column), but we are not entitled to free services. Unless, of course, we’re willing to barter with something else, such as our consumer profiles or our photo streams.

What irks us, of course, is the sense that we’ve been betrayed. Instagram felt a little alternative, authentically bottom-up. It’s a tiny piece of software, and if they had figured out a way for us to store our photos locally or to pay a small charge for server space exceeding some amount (as Flickr does), it could have stayed a rather noncommercial affair.

Moreover, Instagram’s community, perhaps rightly, feels as though it was responsible for its own formation. Even though this community formed around a piece of commercial software, the relationships within it are real and the result of a significant investment of time and energy and trust. Now that those relationships have turned out to be commodities, many people feel exposed and cheated. No longer the users, but the used.

Sorry, but – in a word – tough. This is the way of the Internet: pay or, well, pay. Just as Facebook’s users must come to grips with the fact that they can longer reach all their friends with an update unless they pay for “promotion,” Instagram’s users must reconcile themselves to the fact that their photographic creations are now grist for some advertiser’s mill.

After all the time and energy put into one’s profile or network or photo stream, the ground rules seem to change. And those rules seem to change just at the moment our investment and connections seem too large to make it worth jumping off to some other service, if one exists.

Yes, sometimes it’s hard to learn just where in a company’s business plan one fits. But let’s hope these early experiences of investing in free stuff only to learn the true cost will make us more ready to think twice about when and how we wish to participate. For if we’re not paying in money, we’ll end up paying with something else.