My SIL did for a while. BUT, they were on items such as diapers and things like that. Not food items. More like high-consumption items. We don't use anything to that degree. I looked into it, and for us, it wasn't erstwhile to have our money tied up in 20 rolls of paper towels, where we saved $1 per roll. We have no place to store that many, and it would be about a year's supply or longer!
I have bought coupons off ebay and I have sold them. Personally unless it is a really good deal on items that you use on a regular basis, it is not worth it. It was not worth my time to cut and sell on ebay either.
I find if there is some really good coupons, I tell my DH to get 1 or 2 extra papers, and snatch the coupon inserts from the break room at his work, since he works every Saturday and Sunday.