General Motors was right when it said Facebook ads weren't effective, a Reuters poll finds. Only a fifth of Facebook users say they have ever bought something because of ads or comments on the social network, the poll found—and 34% say they are spending less time on the site than six months ago, while 20% say they are spending more. The poll highlights worries about Facebook's ability to make money from its user base, which is, nevertheless, huge: Only 21% of those polled said they had no Facebook account.
Facebook is still perfecting its advertising, but "comments and recommendations from friends on Facebook do carry a lot of weight, so I'm surprised by the number," says an industry analyst. Facebook didn't comment on the details of the study, but pointed to case studies including Applebee's, a restaurant chain whose Facebook ads delivered a threefold return on investment, according to findings. Facebook shares closed at a new low of $26.90 yesterday, down 29% from its IPO on May 18. (Read more Facebook stories.)