NO checking accounts - referrals for business Platinum cards = 25k miles bonus
Rewards on PURCHASES are not taxable as they are considered rebates - but bonus rewards for opening bank accounts are taxable
And it appears now that the bonuses for referrals are taxable as well
Chase has 1099'd people with $600+ (according to their valuation) in referral bonuses for years. It does seem to match the IRS guidance since it isn't tied to any purchases.
Edit: seems like Chase started doing this about 5 years ago.
https://onemileatatime.com/chase-referral-1099/