I'm quite new to this site. I have been playing Fluxx IRL since the early 2000s but I don't own a deck with this stupid holiday/birthday card in it, so this was new to me. Seemed fun at first, but everyone abusing it has totally ruined the game for me. To the point where I just don't want to play it.
People trying to excuse the behaviour by saying that you have to choose 1/2/3 BEORE seeing whether it's an advantage or not clearly don't understand probability. I mean, let's overlook the fact that you're just plain wrong - saying it's your birthday when it's not is lying and therefore totally against the spirit in which the card was intended to be used, i.e. getting a birthday gift.
But back to probability. I'm not getting into a massively detailed breakdown here, but there are many, MANY more advantageous outcomes by playing 3, than there are negative ones. You people make it sound like it's a 50/50 and there's an equal chance of getting lucky or getting unlucky by lying. But that's simply not true. The cheat option benefits you a disproportionately large number of times and therefore you are incentivised to cheat.
Sometimes, cheating can end the game there and then. It's a hugely dissatisfying way to lose, when you watch it unfold and can clearly see that you wouldn't have lost if they'd played the correct number of cards.
Because people cannot be trusted not to cheat, something should be done. Having the game automatically choose it randomly, as some have suggested, makes no sense to me, but I'd still prefer that to letting people cheat willy nilly. Because then you're at least all bound by the same rules. That's all we really want, to have everyone playing the same set of rules, so it's a level playing field.