While it s delightful to see stocks actually rally for once, when one looks inside the major indexes, it s difficult to find the type of leadership likely to lead a new lasting bull charge.

Within the S&P 500, for example, the biggest components include Exxon Mobil (XOM) (5.32%), AT&T (T) (2.19%) and Procter & Gamble (PG) (2.14%), none of which seem likely to inspire the next new market run. The most promising of the top 10 S&P 500 stocks is Johnson & Johnson (JNJ) (2.11%), which hit an all-time high of $72.26 in mid-2008.

Johnson & Johnson 10 years

The Nasdaq 100, tracked by Powershares QQQ (QQQQ), is still dominated by old tech names like Google (GOOG) (4.49%), Oracle (ORCL) (3.18%), Cisco Systems (CSCO) (3.08%) and Intel (INTC) (2.72%), all of which would appear to have already had their big bull market runs. The most promising of the top 10, at least from a technical perspective, is another health-related stock, Teva Pharmaceuticals (TEVA) (3.09%).

Nasdaq's Brightest:

Teva Pharmaceuticals 10 years

After the Fall

After stocks collapsed last year and rallied last week, investors big and small are scratching their heads, unsure of the best mix of assets to both protect and grow their savings. It s hardly an easy answer.

Regular readers know I don t approach investing with any blind devotion to one asset class. As the past decade has aptly demonstrated, just because stocks have performed well over the long term doesn t tell us how they might perform over our actual holding period, which is likely much shorter than the 70-plus years often quoted in those studies.

To a large extent, our age should dictate our appetite for risk. It s common practice that the older you get, the more you should shift your investments toward bonds and cash. Because older investors need liquidity and lack time, cash is necessary no matter what other assets you may hold, be it stocks, real estate, Beanie Babies or even gold.

But beyond cash, the risks you should take in the rest of your portfolio is more of a function of the current environment than an abject devotion to any one asset class.

Just consider the last decade. In the late 1990s, the predominant winner was undoubtedly technology. Initially investors bought mutual funds, and then more focused funds, then ultimately only the top Nasdaq names like Microsoft (MSFT), Sun Microsystems (JAVA) and Cisco. For a few years, it was all you needed to own. Then the game changed.

From 2001 to 2007, owning almost anything commodity- or real-estate-related was a solid profit center. Mortgage REITs, commercial REITs and residential REITS all rallied. And although it wasn t a straight line upwards, energy-related names ranging from oil services companies to energy trusts to integrated majors and alternatives like solar and ethanol all had their runs. Investors flocked to these ideas en masse. Those days are gone as well.

So what will it be now?

Given the widespread talk of downturn and depression, it very well might be stocks. As we ve noted a few times over the past number of weeks, there s palpable pessimism toward equities right now. Investors are rightfully scared, and collectively they ve dumped a large amount of stock and mutual fund holdings, a traditionally bullish sign for stocks.

It could be industrial metals such as the tin trade I highlighted last week or health-care stocks expected to benefit from an aging America. The next big asset class very well might be something like intellectual property, life-settlements or air rights, markets for which a centralized exchange does not (yet) exist. Right now, the tea leaves simply aren t that clear.

A large part of that uncertainty stems from recent and historic intervention of the government. That political uncertainty renders traditional forms of economic analysis worthless.

For example, we are likely to be subject to some sort of cap-and-trade carbon tax, which is expected to ignite the market for the carbon credits we ve written about over the past few months. The value of these truly worthless slips of paper is decided solely based on government decree. How can one calculate the innumerable factors that go into making large-scale investments in energy without knowing, in a sense, what the rules are going to be?

Bull markets aren t dead, but they re being obscured, distorted and delayed by the presence of big government intervention. When it goes away, the next bull markets will emerge.