NEW YORK (CNN/Money) - Everybody on Wall Street, it seems, is preaching the virtues of playing a little defense.

The time has come for investors to put their money in safer fare. Shift out of those less-than-staid stocks that flew in 2003 and buy some of the stodgy laggards. Consumer staples look good, so do utilities, and everybody loves energy.

What people say and what they do, however, are different matters. In this year's brief tenure it is tech stocks -- particularly ones with big dreams but little earnings -- that are up the most. The Nasdaq Composite is up more than the S&P 500 in 2004 and the S&P 500 is up more than the Dow Jones industrial average. Just like last year.

2004 best performing stock? Lucent (LU: Research, Estimates), which has tacked another 15.5 percent onto 2003's 125.4 percent gain.

It smacks of momentum investing, where traders put money into whatever has been doing best. It's a much-derided strategy, but, of course, it often works well. This may particularly be the case at the beginning of the year, when many investors put their money with the managers who did best the year before (never mind that "past performance is no guarantee" stuff), and the managers, flush with cash, put their money with their old faves.

The result is basically a reworking of Newton's first law of motion: A stock that is in motion tends to stay in motion with the same speed and in the same direction.

This can, as we all learned in 2000, take stocks well beyond where they should be fundamentally. When a sector keeps going up many investors who had shifted out of it experience seller's regret, and begin to question their decision. Meanwhile, others on Wall Street begin to spin theories about why the sector's prospects remain good.

And the chase is on, as everybody piles into the stocks whose rally they thought had exhausted itself.

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But of course the rally does exhaust itself eventually, often abetted by a bit of negative news that investors latch onto. (Remember how Newton's law ends -- the object in motion stays in motion at the same speed and the same direction unless acted upon by an unbalanced force.)

It's at that point, when the market runs into a bit of trouble and people get a little scared, that the rotation from one sector into another occurs. Not before.