Brand Keys, the consultancy, recently updated its annual Customer Loyalty Index, based on a survey of 49,000 people, to ascertain how attitudes are changing in the social media space.
It found that the brand equity score for Facebook, boasting 900m active members around the world, had declined by 7% since February 2012, when it was the top-ranking player in its sector.
As such, Facebook currently occupies fifth place in the charts, trailing YouTube, the video site, Twitter, the microblog, Pinterest, the content-sharing service, and LinkedIn, the business-orientated network.
More specifically, Facebook's "self-image" rating fell by 11%, hit particularly hard by complications surrounding the firm's stock market flotation. Its "trust and security" total also slipped by 20%.
The service's figures remained flat when assessing the "ease of connection" it affords, as was the case for the "brand value and content" reading.
"Five months ago Facebook was doing just fine," said Robert Passikoff, the founder of Brand Keys. "What was once a community is now being viewed as a business, and that changes things substantially."
"Diagnostically they lost connection and friendly engagement in two of the four category drivers that consumers use to make decisions about where their loyalty, time and money will go."
Alexander Chernev, from the Kellogg School of Management, argued Facebook was confronting an analogous problem to "New Coke", a reformulation of Coca-Cola's eponymous carbonated drink in 1985 which provoked an outcry among customers.
"Today, Facebook is experiencing a somewhat similar crisis of confidence. Some of its users feel betrayed by how Facebook is being commercialised," he said.
"Similar to Coke, Facebook has become an integral part of the lives of many of its users and an important means of sharing their individuality with their friends and the world."
Facebook, however, was not the only social media platform in Brand Keys' study to be facing problems, as Google+ fell from fifth spot to eighth in the charts, reflecting mixed reports about its progress.
Data sourced from Brand Keys/Forbes; additional content by Warc staff