I think it's fine as a marketing argument, like in the page where you present your product. As much as citing the big names already using it.
What isn't fine is when you try to book an hotel room and you get nagging messages saying that 2849 other people want to book the same room for the same dates. And of course when you try to unsubscribe and you need to pass through marketing material, with or without social proof.
That's not social proof, that's false urgency, which is its own pattern listed separately.
> Dark patterns involving urgency impose a real or fake temporal or quantitative limit on a deal to pressure
the consumer into making a purchase, thus exploiting the scarcity heuristic. Accordingly, such dark
patterns may also be referred to as scarcity cues or claims. Examples include low stock and high demand
messages or a countdown timer to indicate an expiring deal or discount.
What isn't fine is when you try to book an hotel room and you get nagging messages saying that 2849 other people want to book the same room for the same dates. And of course when you try to unsubscribe and you need to pass through marketing material, with or without social proof.