Illustration by Alexander Ho; Getty Images

A lot of Americans are ticked off at their banks, and a new survey puts some numbers to that sentiment. Consulting firm cg42 says big bank customers will collectively withdraw $185 billion in deposited funds in 2012, and a total of $399 billion is “in jeopardy,” meaning that customers are considering making a switch to another banking institution.

“It should hopefully elicit a re-examination of their offerings, customer service and operating policies,” says Stephen Beck, cg42 founder and managing partner. The study took a look at the 10 biggest banks in the country and measured what it terms areas of “vulnerability,” such as how frequently customers get annoyed with their bank and how often they vent on social media forums like Facebook.

The four biggest banks — Chase, Bank of America, Citibank and Wells Fargo — stand to lose the lion’s share of that $185 billion. According to the survey, they’re on track to lose $135 billion in customer deposits if they can’t find a way to woo new customers and keep existing ones from defecting.

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Bank of America, Citibank and Wells Fargo were dubbed the top three most vulnerable banks by cg42. Most at risk, the survey says, is BofA, which stands to lose $42 billion and around 10 percent of its retail customer base. The company conducted the study earlier this year, before BofA’s poorly-received plan for a $5 monthly debit card fee was announced and then withdrawn after a public outcry. Beck says that if the company re-conducted the survey today, those events would probably be reflected in the results.

“Our expectation would be that Bank of America would have seen an increase in some of its vulnerabilities,” he says. Beck couldn’t say how many more customers would be likely to jump ship as a result, although he adds, “We expect that the findings in the survey are conservative in light of recent events.”

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Bank of America spokeswoman Anne Pace said via email, “We only report account information and deposit balances every quarter as part of our overall financial results, so we can’t speak to any potential impact at this time.”

Beck says customers also called out Capital One for customer service glitches, and dinged Wells Fargo for aggressive upselling. In the case of Wells Fargo, Beck points out that selling existing customers new products and services is something that’s generally looked on favorably by bank management. The response from customers shows that they have considerably less enthusiasm for this practice.