The simple story line from this week’s uprising against Instagram is this: Powerful tech company pushes the line on privacy and sparks such widespread user outrage that it has no choice but to retreat.

Score: Users 1, Instagram 0.

But there is a more complicated story line — one that is much harder to score, and more worrisome for those who regard personal privacy as something of a sacred right.

The tip-off for me came when I interviewed Fordham University law professor Susan Scafidi on Tuesday. She was quite certain that the things users feared most — namely that their images could end up on billboards or other kinds of ads — was made legally possible by Instagram’s planned changes to its “Terms of Use.” But she also said that the old “Terms of Use,” which most of us Instagram users blew past when we signed up for the service, likely allowed the same behavior.

The difference, she said, was a matter of explicitness. Scafidi considered either version of the policy remarkably expansive because Instagram conveyed “non-exclusive, fully paid and royalty-free, transferable, sub-licensable, worldwide license to use the Content that you post on or through the Service.”

That language is still in Instagram’s “Terms of Use” today, even after the photo service announced the reversal in a company blog post Thursday night.

In other words, the issue was never that Instagram could sell your images. The issue was that, under the “Terms of Use,” they could license them to anyone, anywhere, for virtually any purpose.

The main limit on this power is Instagram’s privacy policy, which givers user the ability to restrict access through privacy settings. But it also gives the company the right to share information with what it describes as “business partners, which may include advertising partners.”

And it says that if Instagram is ever sold, “your information such as name and email address, User Content and any other information collected through the Service may be among the items sold or transferred.”

There are sound business reasons for Instagram, and other tech companies, to tread carefully on privacy issues. When users learn of something they consider outrageous, they can raise a stink on social media in a matter of minutes. Facebook bought Instagram in a deal initially valued at $1 billion for Instagram a few months ago, but it would be worth much less if angry users left en masse and stayed away. (Washington Post Co. Chairman Donald E. Graham is on Facebook’s board.)

Polls show that most Americans have little idea how much personal data tech companies already collect and how the data are used. When common scenarios are described, strong majorities of users say they oppose such practices — apparently unaware that they already happen.

Yet we continue uploading pictures and videos, detailing our relationships by declaring “friends” and effectively endorsing products by hitting the “like” buttons that are avidly tracked by advertisers, then compiled by data brokers into increasingly sophisticated and precise profiles of us all.

Tech companies, meanwhile, keep nudging the lines little by little. Sometimes they get pushed back, but rarely all the way back and rarely forever.

Note that Instagram co-founder Kevin Systrom was already preparing the way for this process in Thursday night’s apologetic blog post. Even as he backed away from the current round of changes, he began laying the groundwork for the next one.

“Going forward, rather than obtain permission from you to introduce possible advertising products we have not yet developed, we are going to take the time to complete our plans, and then come back to our users and explain how we would like for our advertising business to work,” he wrote.

So, the process would be different. But it’s not clear that the outcome would be different, too.

To be fair, Instagram is free to users, as are Google, Facebook, Twitter and a host of other cool services many of us love to use. These companies make their money predominantly from advertising, and they make much more money when they can deliver ads that are highly targeted, based on what they learn about people as we use their services.

So there is a trade-off here that most users likely understand: We give up some privacy in exchange for free access to services that enrich our lives.

But in this basic deal is far more fine print that most understand, and as Instagram showed this month — and Facebook showed last month and Google showed in January — that fine print is ever-changing.

All of which reminds me of the old metaphor about the frog and the pot of water: Toss a frog in a pot of boiling water and he’ll immediately jump out. But if you put a frog in a pot of cool water and slowly turn up the heat, he’ll never move.

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