More than one-third (34%) of Americans are "tuning out" social networking sites, with 39 percent doing so because of rude behavior, according to a new survey by Weber Shandwick and KRC Research.

"We prefer to communicate through social networks the same way we do in everyday social settings. We tend to congregate around shared interests. We want to know who we’re talking to. And if there is a difference of opinion, we expect respectful dialogue. If not we tune out," said Weber Shandwick’s President of Digital Communications Chris Perry.

"This reality should be top of mind as companies and institutions increasingly operate in social media. It’s a personal medium. Same rules of shared interest, transparency and respectful discourse apply."

Nearly half (45%) of Americans have defriended or blocked someone online because of uncivil comments or behavior, while 38 stopped visiting an online site because of its incivility. In addition, 25 percent have dropped out of a fan club or online community because it had become uncivil.

The survey asked Americans to rate the civility of 18 aspects of daily life. Blogs rated more uncivil than social networking sites and Twitter (51% vs. 43% vs.35% respectively). While half of Americans say blogs are uncivil, a much larger 72 percent view the political world and government as uncivil.

"Let’s face it. Incivility can be found everywhere today. Blogs, in particular, are mostly open terrain – practically anyone can comment to a post, often anonymously," said Leslie Gaines-Ross, Weber Shandwick’s chief reputation strategist. 

"On the other hand, social networks, such as Facebook, MySpace, LinkedIn and Twitter, are usually tighter communities with little anonymity and greater accountability for who is speaking."