Like e-mail accounts and water at restaurants, checking accounts have become something people are used to getting for free. But that could be changing.

In Bankrate's 2010 Checking Study, the percentage of checking accounts considered "free," that is accounts with no monthly service charges and no minimum balance, fell from 76 percent in last year's study to 65 percent in this year's study. The drop reverses a steady increase of free checking accounts dating back to at least 2003.

What's driving this reversal? Two big regulatory changes for banks are at work here, says Greg McBride, CFA, senior financial analyst for Bankrate.com.

The biggest change right now is a new Federal Reserve rule requiring banks to seek a customer's permission before enrolling them in overdraft protection coverage that temporarily covers purchases at the register in exchange for what's usually a big bank fee later, says McBride. This rule applies to ATM transactions and debit cards, which will now simply decline a purchase if a customer doesn't have the funds in his account to cover it and hasn't opted in for overdraft protection.

Income from debit overdraft fees was a major source of revenue for the banks, $37.1 billion in 2009 alone, according to Moebs $ervices Inc., an economic research firm in Lake Bluff, Ill. That revenue stream will no longer help subsidize the cost of free checking accounts for banking consumers. That's causing banks to rethink their checking account offerings, says Bert Ely, a banking consultant and principal of Ely & Co. in Alexandria, Va.

"Part of the repricing (of checking account fees) is reflecting what I believe is a reduction in the amount of cross-subsidy that's available within banks simply because of a drop in overdraft fees," says Ely. "It's like squeezing a balloon. The revenue balloon is getting squeezed in places, so to get the same amount of revenue, it's got to bulge out someplace else."

But banks are bracing for an even bigger slice to their bottom line from a provision in the Dodd-Frank Wall Street Reform and Consumer Protection Act passed earlier this year. Known as the Durbin Amendment, the provision allows the Federal Reserve to regulate interchange fees, or the fees merchants pay to banks for debit card transactions. Such fees have been another major source of revenue for banks.

"We haven't yet seen the impact of lower interchange fees," says Ely. "I don't know how that's going to play out, but that's a huge question right now."

As the FDIC considers further limits on how much banks can charge in overdraft fees for bounced checks, it's likely that rank-and-file checking customers will be asked to shoulder more of the maintenance costs of their accounts if banks can no longer rely on overdraft customers to subsidize free checking, says McBride.

"There's a fixed cost to (maintaining a checking account). There are regulatory requirements, filing requirements and then there are processing statements, posting transactions and all of those things," says McBride. "What banks have traditionally tried to do is offset that cost by cross-selling consumers into other products and services."