I'll admit it - I placed a preorder yesterday even though I already have previous preorders (including at Walmart). Besides legitimately wanting multiple consoles for myself (I have 2 NES classics, one I play at home and the other I bring along for travel - it's very convenient to bring to hotels or to friends' houses), I also have friends who asked me to get them one if I were able, since they knew I was willing to play the preorder game and spam F5 with the NES classic, and they wouldn't know where to start in terms of getting notifications.
That being said - I don't feel secure about any of my preorders yet just based on past history, so if another preorder came up I might be tempted to try again. I got one in at Amazon... but everyone questions the legitimacy of that listing, and hey Amazon just sent an email yesterday to everyone announcing the delivery date was now undefined. That's not comforting. I got in orders both times at Walmart - the retailer that famously canceled their preorders last month (and even with yesterday's people are questioning whether it was an "error" because the preorder page was different and some orders are being canceled). And so on.
So it's not like the people who have already placed online preorders, even multiple ones, feel secure they're actually going to get anything when the 29th rolls around, which may contribute to a sense of needing to get in multiple preorders just to secure at least one.