For the user: this extension seemingly uses deceptive practices to offer inferior coupon, sometimes inputting their own brand coupon less than a discount than other coupons available while getting commission for theirs. Often, Honey declares no coupons are available even if the user suggests one to the Honey's database.
To other businesses: it steals from content creators or 3rd party websites who gain commissions when using their links when advertising/recommending by secretly swapping cookies at the last second before purchase. Either is does this by opening a quick pop-up window which it then closes before the user sees, or clicking the button "got it!" to dismiss the window Honey shows when it prompts that it doesnt have coupons available.