(Dow Jones) The recent SEC complaint against Goldman Sachs Group Inc. has brought newfound attention to the "fiduciary standard"-namely, the idea that some financial advisors put clients' interests at the fore of every investment decision, while others work on a standard that simply ensures clients are offered "suitable" products.

But what if the client insists on investing in something that makes little to no financial sense to the adviser--say, stock in a company that sells snow shoes to surfers?

Therein lies one of the great dilemmas for true fiduciaries. And industry pros and observers say there's no standard or one-size-fits-all solution, especially since even "bad" investments can sometimes turn a profit.

In the most extreme cases, advisors will rebuke the client altogether and suggest they take their entire portfolio to another firm. That's often because the client wants to commit a significant portion of their portfolio-for example, 50%-on what the advisor deems a foolish bet.

Otherwise, if the adviser were to play along, it could have financial, legal and ethical consequences down the road, says Alex Potts, chief executive of Loring Ward International Ltd., an asset management firm based in New York. "It's like you're an accessory to a crime," he said.

If the amount of money the client wants to commit isn't as large-and if the investment isn't as risky-some advisors will agree to make and manage the investment on the client's behalf. But they will cover their legal bases by documenting-with a waiver or simply an email that recaps a discussion-that they warned against such a purchase.

Still, what's an acceptable amount? Kelly Campbell, a certified financial planner in Fairfax, Va., says investments that represent 1%-2% of a client's portfolio are generally within reason. If the figure starts approaching 5%, he's more hesitant.

At the same time, Campbell won't send them completely packing to another firm. Instead, he might suggest they open a separate account with a discount broker to handle the particular investment.

Matthew Tuttle of Tuttle Wealth Management in White Plains, N.Y., advocates a similar approach with clients, but puts it in blunter terms. "I can't stop them from being suicidal, but I will not give them the gun," he said.

Still, when advisors believe it's acceptable to go along with a "bad" investment, the matter is muddled by another point: Why does the client want it in the first place? It may be for sentimental reasons-say, it's a company that makes a product the client has long liked. Or in other instances, it may be because the financial industry itself has misled the investor through false or dubious marketing.