Steve Goldberg of Tweddell Goldberg Investment Management in Silver Spring, Md., noted that if Gross can't use his unique gifts for identifying undervalued bonds as a way to outperform the competition, his ability to stay a step ahead will depend entirely on his macroeconomic market forecasts being right.

"Pimco has done better than any other firm in getting its bond calls right," Goldberg said, "but every market cycle makes someone look like a genius, only to lose it and look like a fool in the next cycle. . . . It's tough to make a living, or a mutual fund that is better than all the others, when your only way to add value is to have every market call be right, because no one -- not even Bill Gross -- is right all the time."

Goldberg also noted in a story he wrote on the Kiplinger website that "with the fund so big, the natural tendency is to play not to lose. After all, if you give investors decent performance, they probably won't bail out, even if they can do better elsewhere."

And the point is that, going forward in the bond space, investors most likely will be able to do better elsewhere, by picking lower-cost funds run by managers who are doing the things now that made Gross' fund famous in the first place. Pimco's expense ratios for Total Return are no better than average, which seems ridiculous for a fund so large, and its prospects are worse.

You buy this fund for Bill Gross, but, at its current size, he can't actually do much to affect performance.

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"He talked at Morningstar about entering a period when interest-rate duration plays are not going to make it, so if you want to make money in bonds, you will have to make plays on credit risk," Goldberg said. "But the days when he can turn those plays into something that really makes Pimco Total Return continue to beat the average bond fund by so much are gone."

With that in mind, you might want to follow Gross' advice and diversify into bonds from Brazil, Canada and Germany, and into high-quality, dividend-paying stocks. But you don't want to diversify your holdings by owning his Total Return Fund.