Yes indeedy, it is possible to overfeed a cat! Assumpta is completely neurotic about food, probably from being a stray (she's actually gaining weight on about 180 kcals per day). If given the chance, she'll eat herself sick, throw up, and start eating again. Even with timed, measured feedings (which I highly recommend), she'll still bolt her food too fast sometimes and throw up (though we haven't had this problem with wet food). Some people suggest putting golf balls in the food bowl to slow down the speed of eating to help with that problem.
Oooh yes, you can absolutely overfeed a cat. Often we spoil our kittens and growing kittens seldom become obese, but when they stop growing we simply forget that the cat will need less food. Not more than 5 % of the cats total food intake should be treats.