I don't know... If I had to guess, this sounds more like incompetence than malice to me.

Not a chance. Even at scrappy startups, these offers are carefully evaluated by lawyers to comply with necessary laws. There’s no way their lawyers looked at this and just sort of forgot to catch the lack of a “one per customer” clause.

It’s not really malice, though. They simply wanted to buy their way to the maximum number of signups they could get, and paying customers to sign up is the easy button to do that. Removing the limit for multiple signups will take it even further.