Guidance bumps are powerful things. Sweeten the projected pot, and you'll send a stock soaring; go the other way, and pull the rug out from unsuspecting investors. Some companies would be better off not playing the guidance game at all. Logitech International (Nasdaq: LOGI) is one of them.

The maker of PC peripherals and entertainment-enhancers keeps poking at its outlook for fiscal year 2011, pulling its poor shareholders up and down with reckless abandon. Today, Logitech's stock fell as much as 18% as management brought the latest upgrade back to an earlier, less optimistic, target range.

The company now expects full-year sales to land slightly above the $2.35 billion mark, down from a $2.4 billion outlook from the end of January and largely back to the numbers projected back in October. Management blames soft demand in the EMEA region. In all fairness, Logitech CEO Gerald Quindien called the recovery process in Europe "uneven" in the January earnings call, but then maybe he should have left his guidance range wide open in order to account for that variable.

Fellow hardware wrangler Texas Instruments (NYSE: TXN) is another guidance-happy guppy that updates its forecasts more often than strictly necessary, with sometimes-disastrous results. On the other side of the argument stands Apple (Nasdaq: AAPL), which rarely issues a forecast it can't guarantee to obliterate, and Google (Nasdaq: GOOG), which doesn't do guidance.

Management forecasts sure make life easier for analysts, particularly if taken as gospel, but they don't always mean all that much. And then you get revisions or outright misses, which leads to a crashing stock chart. I say, leave the guesswork to the analysts and let management focus on just running the business -- or else set the bar low enough that it really doesn't matter.

Logitech's real fourth-quarter report is due by the end of the month. Make sure you don't miss it -- add Logitech to your watchlist by clicking here right now.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.