Perhaps the most compelling reason for a business to get on Facebook is the likelihood that its customers are already there — and talking about it.

Charles Nelson, president of Sprinkles Cupcakes in Beverly Hills, said it’s crucial to pay attention to what people are saying about your business online. He and others at Sprinkles respond to every person commenting on its Facebook page.

“Requests. Complaints. We’re watching. It’s not just me, it’s our entire team — store managers, the corporate team — who are paying attention,” Nelson said. “If you think about it, businesses used to have a small suggestion box near the door that mostly housed dust bunnies and an occasional piece of gum. Rarely would someone get back to you. But people can now make a post from an iPhone or a BlackBerry while they’re sitting in your restaurant.”

Nelson and other businesspeople offer other tips:

* Use your expertise to promote your business.

Jeweler Janet Rothstein writes about the danger of unsanitary ear piercings, or the effects on jewelry sales of the price of gold, and finds that those posts increase traffic to her sites — and her store, J. Rothstein & Co.

* Be careful about putting too much personal information on the site.

“That’s an issue of the fuzzy boundaries between the public and the private, and how much do we use our own network,” said Michael Liskin, who specializes in social media at Plus Delta Consulting in Los Angeles. “These are questions that are open and not been worked out yet.”

Different people approach the issue differently. Attorney Thea Beatie Eliot posts photos of her children, saying that other mothers “are my target market, and I want them to see that side of me.”

Ed Poll, who runs LawBiz Management Co. in Venice and has a page at www.facebook .com/LawBizManagement, with 217 fans, remains circumspect.

“When you go on the Internet, it’s permanent. There’s no such thing as deletion. You really have to be careful what you say,” he said.

* Remember that ultimately, Facebook owns the site and can change the terms of service.

Earlier this year, Facebook decided to revoke certain rights to generic names such as “wine,” or “tea,” or “beach.”

Although Facebook says those URLs were largely populated with spam, some were legitimate. The ban affected someone known as WineGuy who ran a site at www.face book.com/wine, where he had more than 750,000 fans.

Facebook restricted that particular vanity URL last month, although it did allow WineGuy to write a farewell post to his fans, directing them to another site, at www.face book.com/winesearcher. The page has about 77,000 fans, or about one-tenth the number of fans of the old URL.