Facebook's latest quarterly report with the SEC contains a little-noticed update to its risk factors.

For the first time ever, Facebook acknowledges that concerns about users' well-being could hurt its business.

It's a striking change from the company's altruistic boasts of the past.

Facebook CEO Mark Zuckerberg has talked a lot about making sure that users' time on his social network is "time well spent."

After a year of headlines blasting Facebook for negatively affecting everything from mental health to memories, Zuckerberg was responding — and, he said, showing responsibility — to growing public concerns about the age of social media.

But as Facebook revealed in a tiny but telling change to its latest quarterly report, the company also appreciates the very real threat these concerns pose to its business.

"Any number of factors could potentially negatively affect user retention, growth, and engagement," Facebook explains in the section of its 10K report devoted to risks related to its business. If, for example:

— "there are decreases in user sentiment due to questions about the quality or usefulness of our products or our user data practices, or concerns related to privacy and sharing, safety, security, well-being, or other factors;"

We bolded "well-being" to highlight the two words because they were not included in the same boilerplate sentence in the report released three months earlier. Go ahead, check for yourself.

Sure, regulatory filings to the SEC are kitchen-sink exercises, with every potential risk a corporate attorney can dream up explicitly spelled out. The company isn't saying it expects any of these risks to actually occur in the near future; it just wants to be able to say it warned you they might occur in case you ever decided it might be a good idea to sue the company.

That said, Facebook never thought its impact on people's well-being was a notable risk before. To the contrary, the company couldn't stop bragging about its altruistic "social mission."

Remember Zuckerberg's letter to shareholders in its IPO prospectus. Here's an excerpt, with emphasis his:

"We hope to strengthen how people relate to each other.

Even if our mission sounds big, it starts small — with the relationship between two people.

Personal relationships are the fundamental unit of our society. Relationships are how we discover new ideas, understand our world and ultimately derive long-term happiness."

It's been seven years since Zuckerberg wrote those words, and 15 years since the social network was created. A lot has changed in that time. But sometimes two small words buried in a dense regulatory filing say how much has changed better than anything.