Depends on how many plants we're talking about, and the jurisdiction in which you're growing. In most places, they usually won't bother busting anyone for just a few plants, simply because they can't afford to pay cops overtime for days and weeks on end to stake out a grow. Of course, if they happen to come across you just when you're staggering out of the woods with a half dozen plants, they won't waste the opportunity to bust you, but for the most part, if they stumble across a small grow they'll just rip 'em up and be done with it.
If you're talking 20, 30, 60 plants, well... that's a different matter. They like busting large grows, because it makes them look all heroic and shit. Stay small, and they'll cruise right by you looking for bigger fish. And in some backwater, redneck areas, they will go to considerable lengths to bust someone growing a half dozen plants, simply because they've got nothing better to do with their time. But that's rare. Usually, small grows slide by right under their radar.
peace man