The number rises to 54 percent for people under 25 years old, and owners of smartphones are more than twice as likely to post something they wish they had not, according to a new poll.
"The information people post to sites like Twitter and Facebook can easily go on to have a life of its own," said Jennifer Jacobson, a social media analyst at Retrevo.com, a consumer electronics review and shopping site, which commissioned the poll.
"You don't always know who's following you and just about anyone can take a screenshot of your post, save it, and share it with the world."
Weiner resigned on Thursday after admitting he had sent lewd photos of himself to women online. He is the third member of the Congress this year to step down over a sex scandal.
The survey of 1,000 people showed that regret postings are up slightly from a year ago. Three percent of respondents said a tweet or post had ruined their marriage or relationship, while six percent said it had caused problems at home or work.
Jacobson said the survey underscores the dangers of social media among people who feel they want to be connected all the time. While some problematic postings can be removed or repaired, some people find damage control challenging, if not impossible.
As smartphones and other mobile gadgets become more available, the desire to share may also increase.
"Maybe the filter that you shouldn't share something becomes numb," said Jacobson.
Fifteen percent of people with so-called poster's remorse said problems arose from their postings, but they were able to remove them, while 11 percent had no problems.
Smartphone users, with iPhones especially, tend to be more trigger-happy than others, and are 26 percent more likely to post something they regret, the study showed.
About 51 percent of iPhone owners have posted something they regretted, followed by 43 percent of Android owners, and 45 percent of BlackBerry users.