Users expressed dissatisfaction with advertisements. There's also growing concern about privacy.
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Overall, social media improved a bit since last year, up 4.4 percent. Pinterest is the clear favorite with an ACSI score of 76, the first time the site has topped the social media category in this survey.
"Pinterest is easy to use; they've done quite a bit in recent months to improve the functionality of the site; and they're definitely head and shoulders above some of the other really big guys out there," VanAmburg told CNBC.
Other major players: Google+ had a 71. Twitter jumped 6 points to 69, its highest score to date. This follows a site redesign that makes it easier to integrate photos and video. Even though Facebook and LinkedIn improved since 2013—both are up 8 points—they remain tied at 67 for the least-satisfying social media sites. "It's great to see that we've made improvements in the ranking," LinkedIn said it a statement. "Clearly more work can be done, and we are actively looking into more ways to improve the LinkedIn experience."
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