WSJ columnist Ron Lieber ran some quick numbers on BofA's latest foray into brokerage business. His conclusion: only active traders will benefit from the free trades associated with $25,000 deposit.

To answer it for Bank of America, check some of the finer print in its offer: The only free trades are the ones you make online; you can't use a broker. Then, you need a cumulative total of $25,000 in "deposit" accounts. Your stocks and mutual funds don't count. Here's what will: checking, savings and bank money-market accounts; certificates of deposit; small-business deposit accounts; and individual retirement accounts that only contain FDIC-insured products like CDs.

It's a long list, but $25,000 is a lot to keep in cash-like vehicles. That's particularly true given that Bank of America doesn't offer the highest interest rates in the land. If you could do one-half of one percentage point better anyplace else, in a year you'd lose $125 for every $25,000 invested at the bank.

That $125 would pay for a dozen or so trades at many of Bank of America's competitors. Given that over half of all brokerage customers make five or less trades per year, according to Dan Schatt of research firm Celent, they'd do just fine by staying put.

For those who buy and hold mutual funds, it's worth considering another factor: While stock and exchange-traded funds qualify for the free trades, not all mutual funds do. BofA's brokerage arm lets customers trade over 1,200 funds free, though here too it isn't the most generous industry player.

Still, active stock traders who, for whatever reason, need or want to keep lots of cash on hand, could benefit here. Also, a cash-hoarding investor who also rebalances a portfolio stocked with ETFs twice each year might save money on those trades. Then again, they could make more by going elsewhere and setting up an online savings account for their cash that pays more than Bank of America does on its accounts.