For the past decade, gold has grown ever more prominent in the investing zeitgeist. "It feels like it's America's pastime now," says Stuart Rosenthal, chief executive officer of Factor Advisors, an asset-management firm in New York. But after flirting with the $2,000-an-ounce mark this summer, the metal's price promptly tanked this fall -- at one point, dropping 9 percent in a week. The slump has left some investors in this $1.9 trillion market questioning how much gold should be in their retirement portfolios...if any.

The yo-yoing in price, say analysts, is a result of gold's sensitivity to the ongoing debt issues in Europe and to the overall weakness of the global economy. Experts attribute the metal's recent violent pullback, meanwhile, to what Wall Streeters call a "liquidity situation" -- that is, traders had to sell their holdings in order to raise cash and cover losing investments.

Still, over the long haul, say many pros, gold looks attractive, as developed governments continue printing money and interest rates stay low (the Federal Reserve has said it plans to keep rates level until at least mid-2013). "I'm not sitting here in denial that the gold price can't go down, but we'd need a big bump in interest rates -- and that's not happening," says David Nadel, comanager of the $464 million Royce Global Value fund. For investors, experts still recommend at least a small allocation of gold in retirement portfolios, despite its current volatility, as a way to diversify and hedge against inflation. Many pros suggest dollar-cost averaging: Adding a set amount to a portfolio on a regular basis -- quarterly, for instance -- allows investors to buy more gold when the price is low and less when it's high, says Nadel.

To get that exposure, investors have a variety of choices, ranging from exchange-traded products backed by physical gold, like SPDR Gold Shares (GLD), to jewelry and gold bars, to stocks of companies that rely heavily on the gold price, such as gold miners. Many of the mining stocks, which have underperformed the actual metal so far this year, could cash in if gold's price resumes climbing or if the miners can keep their costs in check, analysts say. How high can gold actually climb? That, it seems, remains a $1.9 trillion question.