You know, I think I might have a bit of an origin for this legend. On "Cops" and FOX News and all that trash, when they talk about a methlab they talk about how it's "contaminated". Hell, I read about one person doing a reaction in a photo canister in his pants (fucking dumbass) while he was driving. The thing heated very much, popped, and they're going to destroy the car because it's "contaminated", as if the byproducts are a virus that clings to stuff or something.
Considering most of the reactions used by these guys use common chemicals, it seems silly to think that a lab will be any more contaminated than your house would be if you dumped some ammonia and matches around
And that whole "5 pounds toxic byproducts for every pound of meth" is silly too. The most common method is a straight Birch reduction of pseudoephedrine . . . so you'd be using Ammonia (prepared from ammonium hydroxide), Lithium (AA batteries), Red Phosphorus (matches) and Pseudo/Ephedrine. You'd be left with some solvent (usually Diethyl Ether, a bit bad for you but it's found very commonly) and maybe some left-over reagents/catalysts.