Is there any downside to stacking receipt-scanner apps?

As far as I can tell, Ibotta and Fetch Rewards are the most worthwhile receipt scanners. I wouldn't want to get banned from either one - would they be upset if I was using both?

Are there other ones I can stack too? The combination of these two, combined with credit card cashback, couponing, and bottle deposits, could make a serious dent in my grocery bill