  We study linear power corrections ${\cal O}(\Lambda_{\rm QCD}/Q)$ to certain
collider observables. We present arguments that prove that such corrections
cannot appear in observables that are inclusive with respect to QCD radiation,
such as total cross sections as well as rapidity and transverse momentum
distributions of color-neutral particles. Although our calculations are carried
out in a simplified framework, our arguments and conclusions are applicable,
with some reservations, to processes both at lepton and hadron colliders. We
also show how an improved understanding of the origin of linear power
corrections allows us to simplify their calculation. As an application, we
compute the leading non-perturbative corrections to the $C$-parameter and the
thrust in $e^+e^-$ annihilation in a generic three-jet configuration.
