Illusion of Safety

Today I found out that my friend's car key opens my car door. Really. And I didn't even have to force it. What the hell?! Could it be that car manufacturers only have a finite number of keys that they use for car doors? Like maybe 5? That they have misled the car-buying public into thinking that their cars are impenetrable and safe and custom-tailored just for them? Maybe they think, "What idiot is gonna try this key in another car? Let's cut costs and just use it for every model! Genius!" Could it be that in actuality my car key could open any Honda I see on the street? Because if this is so, I really like the Honda Element, so if you've got one of those near my house you should watch out.