Banks are still juggling how best to use social media to communicate to customers — especially when other systems go down.

At around 7 a.m. Friday, Bank of America Corp. experienced a partial outage of its online banking service. The Charlotte, N.C., bank used Twitter to get the word out, but it did not announce the outage on its home page. Impacted consumers simply got an error message.

"It is helpful if the bank sees [social media] as a part of their other communication channels," which should also include branches, call centers, the Web and mobile, said Stessa Cohen, research director for banking industry advisory services at Gartner Inc. in Stamford, Conn.

"It is part of a holistic plan to deal with operational risk events," she said.

Over Twitter, B of A broadcast this message: "Online Banking Outage: Bank of America is working to restore capability as quickly as possible. We apologize for any inconvenience."

It also replied to individual Twitter users with a similar explanation. Though it reaches more than 7,000 Twitter followers worldwide, B of A spokeswoman Tara Burke said the bank opted not to put a message on the Web because the outage did not affect all customers. "Every situation is different and we determine on [a] case-by-case basis," Burke said. She said B of A also informed call centers about the outage.

Burke said the outage was likely the result of routine system changes the bank performed the night before and was not a sign of a security breach or a malware infection.

Cohen said the problem with making the announcement on the Twitter page was that it reached a smaller number of customers than the number affected — but Twitter was still a good start. She pointed to the dangers such outages cause when information is not so forthcoming, such as happened to JPMorgan Chase & Co. in September 2010 when its site went down for a full day.

"Chase did not get the word out well, and it was really criticized for being too slow" to do so, said Mark Schwanhausser, senior analyst for multichannel financial services at Javelin Strategy and Research in Pleasanton, Calif. Transparency is crucial to banks fostering good customer relationships, he said.

"Let the consumer know where they stand," Schwanhausser said.

"The consumer counts on the bank, and if the bank goes quiet, it creates anxiety," he said.

Ron Shevlin, a senior analyst at Aite Group LLC, said lack of that messaging may be because the public website was impacted as well. "Bank of America is a smart bank that has been doing [online banking] a long time," he said. "If there is no message on the home page, there is a good reason." Shevlin said he could not access his own account Friday.

James Van Dyke, the president and founder of Javelin, said the lack of a home page message could be related to the complexity of B of A's systems. "Bank of America's [online system] is actually a combination of several different systems owing to their [acquisition of] prior separate organizations," he said. "So the challenge faced by their professionals is larger than one faced by a community bank or credit union."