What do you mean with stolen? Someone making something similar or making unlicensed copies? For the former i do not see how web apps prevent that and for the latter that only matters when the developer asks for money for each license, which is extremely rare with web apps anyway (the closest is subscriptions and rentals but that happens with desktop/native applications too, e.g. see Adobe and Autodesk). But even that is really a facet of the heavily developer biased control i mentioned that web apps provide.