The simple answer is that if you could snoop enough codes, you could break the signal, there are a lot of after market jobs that have a single signal for locks and one for starts, it just switches the function every time the signal is received by the car. the hardest part is sorting out the signal from all of the other noise, but it wouldn't be impossible.
Code hoping only works when the remote and the base can communicate, and if you could intercept that, you could break the sequence. its a matter of time really, no one is going to pay for a remote lock that cannot be broken when 99% of the time no one is looking for that vulnerability. it's the same for wireless routers, there was no need to change until everyone and their grandma could hack it.
I drive a 92 sunfire, its so ugly that I'm sure a thief would be embarrassed to steal anything, I just hope they use the door handles when the take a look-see.

all locks can be broken into, the trick is to have just a little more lock than someone else.