(CNN) -- If you've got a question about buying a camera, shooting out a quick note to the retailer on Facebook might help. But if you're in the market for a silky camisole? Maybe not.
That's according to a survey of 20 top online retailers on Facebook that suggests their level of responsiveness to customers is uneven, at best.
One out of four companies failed to respond to a customer-service question posted on their Facebook wall, and even fewer replied to questions asked as comments on their posts, reported STELLAService, a company that rates customer service among online businesses.
The results of the survey of 20 leading retailers, conducted on February 29, come at a time when almost every company that deals with the public is trying to tap into the more than 850 million people who use the social-networking site.
"Brands are doing an enthusiastic job of bringing people to their pages," said Jordy Leiser, STELLAService's co-founder. "[But] I don't think they're also necessarily bringing with them a desire to be social. It's just turning into a marketing message for many companies."
Leading the pack was B&H Photo. The New York City-based outlet, which claims to be the largest nonchain camera store in the world, responded to its wall post in about two minutes, according to the report, which was shared with CNN Tech.
Bed Bath & Beyond, Williams Sonoma, Sur La Table and Footlocker all responded to posts within 30 minutes.
On the opposite end of the spectrum, Victoria's Secret, your best bet for the aforementioned camisole, was one of five companies that didn't respond to a wall post within two days. One Kings Lane, Radio Shack, J. Crew and Rue La La were the others.
"Retailers need to realize that two days in Facebook time is like two years in real time," Leiser said. "Customer questions on Facebook should be granted the same urgency as a phone call."
Leiser noted, however, that the survey wasn't meant to embarrass companies or suggest that some of them don't care about their customers. Instead, he said, it was an effort to start setting expectations for an area of marketing and customer service that remains relatively unexplored.
"I don't think we as customers really know what to expect yet if you post a message," he said. "Do you expect them to get back in 10 minutes or two hours? Or, a day -- is that alright? We're trying to develop the standard, or at least identify what the averages are for certain categories."
Among the companies that responded to questions during the survey, the average was under an hour, he said.
The posts were what Leiser called generic product questions: "Do you guys have this in a particular color I don't see? What's the return policy for this particular item ... ? That looks really cool, do you have this in whatever size?"
While 25% of retailers didn't respond to wall posts, that number rocketed to 65 percent for comments on other posts. Eight companies deleted the questions that were posted on their walls, whether they answered the question or not.
Five companies out of 20 -- B&H Photo, Gap, Bed Bath & Beyond, JackThreads.com and Williams-Sonoma -- responded to wall posts and comments and had not deleted those questions within 48 hours.
Only six of the 20 companies listed on their Facebook pages an e-mail address or phone number by which customers could contact them, the report showed.
"You can't just be there halfway with marketing," Leiser said. "If you're going to be part of the community, be part of the community."