In a worrisome sign for Facebook, which is set to release its first quarterly earnings report as a public company next week, a new poll suggests that user satisfaction on the social network may be in a downward spiral. According to the American Customer Satisfaction Index (ACSI), users are increasingly dissatisfied with Mark Zuckerberg's social network, while competitors such as Twitter and, remarkably, Google+ fared better. Here's what you should know:

How was the survey conducted?
The annual report measures 230 companies across multiple sectors, assesses how happy customers are, and then assigns a score on a scale from 0 to 100. Facebook got a 61 this year, down from 69 in 2011 and the lowest score of the "e-companies" included in the ACSI.

Why is Facebook's popularity plummeting?
There are three big reasons, says The Huffington Post: Concerns over privacy, a frequently changing interface, and in-your-face advertising. The introduction of Timeline, in particular, seems to have Facebook users flustered.

How did the competition do?
Google+, which has been disparaged as an unpopular "ghost town," emerged with a "surprisingly strong score," says Fox News: 78 out of 100. The survey's administrators cite Google+'s absence of traditional advertising and what many consider to be a better mobile experience as the primary drivers behind user satisfaction. (Also, it should be noted Google+ has a much smaller user base than Facebook; arguably, only the most satified users have stuck with it.) Twitter had a slightly better score than Facebook at 63, and newcomer Pinterest scored a 69.

How did social networks do compared to other industries?
Badly. On average, social networks are consistently among the lowest ranked industries, beating out only airlines, subscription television service, and newspapers.

What does all this mean for Facebook?
Facebook should feel pressure to improve customer satisfaction right away, says Larry Freed, whose analytics company, ForeSee, partnered with ACSI to release this survey. "It's got to hurt Mark Zuckerberg's ego to see another low rating, considering the company's mantra is about making users happy over advertisers," says Donna Tam at CNET.

Sources: CNET, Fox News, Huffington Post, PC World