Michael Scarborough, president and CEO of Retirement Management Systems, had a few choice words to share about brokerage windows, including having seen a lot of "misuse," especially by people trying to make up for not saving enough earlier in their careers, people "hoping to shoot the lights out in the gym."

Taking care with his words, Scarborough spoke of the "poor effects seen in the past few days," a reference to the beating many investors suffered thanks to the stock market's decline of late, especially that stomach-turning nosedive Wednesday.

"My perspective is that the vast majority of people have no clue," he said. "At the end of the day, if you're going to allow them to do this, you need to give them access to some source of investment advice so they can use it to make better account decisions."

Even with that advice, it can be much like swapping a pistol for a machine gun, Scarborough said. "You can make a whole lot of mistakes very quickly. We're seeing that happen often."

His co-presenter, Michael Ponce, a VP at TD Ameritrade Institutional, offered his own words of caution.

"This isn't for everyone," he said.  

Indeed, it is not, and nor should it ever be.

There is, however, interest building and so unless regulators step in and put the brakes on them, the share of plans that give participants access to self-directed brokerage accounts will likely continue to grow. In 2013, 40 pecent of large and midsize employers offered brokerage windows, up from 18 percent in 2007, according to benefits consulting firm Aon Hewitt.

The participants typically most interested in an SDBA are those with higher account balances, those in the C-suite or close to it.

I'm not worried about them. Their investments can tank and they'll still be able to pay the mortgage and feed the kids. It's everyone else I'm concerned about and, yeah, I know that sounds slightly patronizing and paternalistic. But it's not. It's actually a viewpoint rooted in a more selfish concern that we'll end up with an even larger number of elderly folks to support unless we set some boundaries.

Earlier this year, the Department of Labor said it wants to get a better understanding of how brokerage account windows are used. A lot of people believe that what will emerge from the DOL is unlikely to be favorable to brokerage window fans.

I'm glad for that.

For now, however, if you're a plan sponsor that has either already gone this route or are considering it, another of the panelists Thursday, ERISA lawyer Marcia Wagner, offered a few tips.

She started by noting that while the fiduciary prudence standard applies to SDBA selections, sponsors have no duty to monitor or supervise use of SDBA by unsophisticated participants. That's a relief, I guess, especially for the sponsor that doesn't really care for the welfare of its workforce.

The best practices, she said, include using an SDBA election form stating clearly that investment results are the participant's responsibility. Also, advisor agreements should clearly state whether or not the advisor has SDBA responsibilities.

As long as the broker-dealer is paid reasonably and commissions aren't exorbitant, the plan sponsor has little to no liability, she said.

On a practical note, Ponce suggested that if more than 5 percent of a plan's participants are in the SDBA, sponsors might want to look at their core investment options to see whether some changes can be made to keep participants out.

All of that is fine and good, but I'd say if you don't want people day-trading away their lives or leaping out of windows when the big correction comes, just keep the window down. Not shut, but perhaps mostly so.