Facebook has nearly one billion members worldwide, and brands—the smart ones, at least—are embedded among them and will be for some time.

That means the social network will not shrivel and die anytime soon.

But Facebook has suffered some lumps in recent days and weeks. Its stock price continues to trend downward, and GM plans to pull all of its Facebook ads. And now a new study could inspire more brands to retreat from Facebook.

A Reuters/Ipsos poll found that four out of five Facebook users haven’t bought anything as a result of advertising or comments on the social network. (Facebook responded to Reuters by sharing several examples of brands that successfully launched ad campaigns on the social network.)

The study also found that 34 percent of Facebook users are spending less time on the site compared with 20 percent who are spending more time.

Twitter, meanwhile, has seen a sharp increase in daily use. According to Pew Research, the percentage of online adults who use Twitter is 15 percent, a number that’s nearly unchanged from a year ago when it was 13 percent. However, the percentage of adults who use it on a daily basis has doubled to 8 percent, from 4 percent. The percentage of people in the 18 to 24 demographic joining Twitter jumped to 31 percent from 18 percent.

Compare those figures with Pew results from November 2010, when 8 percent of adults used Twitter and a mere 2 percent accessed it on a typical day.

An eMarketer report from March found that Twitter’s growth is outpacing that of Facebook. However, the number of Facebook users dwarves that of Twitter users. There are about 152 million Facebook members in the U.S. compared with 38 million for Twitter.