Ebates/Rakuten partnered with American Express earlier this year to let you earn Membership Rewards points for your shopping, instead of the standard cashback. Many people value Membership Rewards much more than 1 cent each, so this could be a better option. However the Membership Rewards earning accounts were initially available only to those who have a personal American Express credit card.
But now it looks like all American Express credit cards qualify. So if you only have a business card, then you can sign up as well. The offer is also showing under promotions in the online login. It also shows a bonus of 1,500 points for signing up for an Ebates Membership Rewards account.