Social media is a great way to keep in touch with old college buddies. Or to lose your job. Or to get yourself hauled before a judge.

The power of social media, and the pitfalls, has been particularly evident in the past couple of weeks, as a Chamber of Commerce executive stepped down from her job after questions about her use of Twitter, and a juror faced contempt of court because of something she posted on her Facebook page during a trial.

Both are wiser now, and hopefully others have learned something from these situations as well. Social media is not to be used carelessly.

In Dexter, the chamber executive director resigned in late August after a column in the Dexter Leader questioned how she was using Twitter to promote a campaign aimed at getting people to shop and dine locally. She told AnnArbor.com that the campaign was sound, but acknowledged that she was a novice to Twitter and her efforts to use it were amateurish. “Quite frankly,’’ she said, “I wasn’t that good at it.’’

At least she didn’t run afoul of the law. In Mount Clements, a 20-year-old woman was removed from a jury after she wrote on Facebook that it was “gonna be fun to tell the defendant they’re guilty.’’ At the time, the trial was still proceeding. Her remarks were discovered by the son of the defense attorney, who had been looking up the jurors on Facebook.

The attorney’s son was clever enough to understand Facebook, and to use it in a way that was advantageous to the defendant. But people who engage in social media aren’t always so wise, and naïveté or misuse of deceptively powerful tools like Facebook or Twitter can backfire.

In both of these cases, people got in trouble for remarks that - made privately - would not have had such serious consequences. But on the Internet, even the most innocuous remark is there for anyone to see, and the tradeoff for such reach is a surrender of privacy.

Often, people may underestimate, or even be uncomprehending of, the degree to which their privacy is being compromised online. The Wall Street Journal reported the results of an investigation last week that found if you visit some of the most popular web sites in the United States, you may have hundreds of “cookies’’ or other behavior-tracking devices installed on your computer. While Wikipedia did not install any such devices on the computer of someone visiting the site, there were a dozen other sites that installed more than 100 devices each, according to The Journal.

These devices, which gather information that can be used to target marketing messages, are becoming increasingly sophisticated. Yet most computer users passively accept such intrusion, not bothering to wade through the dense legalize of the site’s privacy policy - if that policy even acknowledges the way that personal information is being gathered and used. Cookies are not inherently nefarious, and many are simply tools that help the user navigate a site, but web sites have an obligation to use cookies responsibly and transparently, and users need to educate themselves about how their computer activity is being tracked.

Much the same, users need to educate themselves about social media. For many people, the mistake is failing to understand distinctions between their personal life and their professional life in the way they use Facebook or Twitter.

If your use of these social media tools is purely personal, you have to consider what may be too personal. If you’re a college student getting ready to enter the job market, you may want to think about what all those photos of you playing beer pong say to a prospective employer. If you’re posting observations about the great time you’re having in Europe, you might think about whom you’re inviting to break into your house while you’re out of the country.

For professional people, social media can be a wonderful means of promoting yourself and connecting with customers. It also can be a minefield, particularly if you’re not well versed in the use of it. Mixing personal remarks with job-related communications also can send a mixed message, either trivializing your professional image or causing the people who follow you to feel they are being spammed.

Anyone can blunder, but social media greatly magnifies the mistake, and the consequences can be more than you bargained for. As much as the Internet has changed the world, some things haven’t changed. There’s still no substitute for exercising good judgment.