You're totally right about the pains with ingredients normalization - I've spent at least two months making scripts to scrape recipes, and it will only match the ingredients accurately about 80% of the time, leaving a lot of work in hand curating everything it scrapes. I ended up trying to promote users to enter recipes by offering a month free every time they entered 5 good recipes. I built up a decent recipe database this way, but it does need to be much larger to better target people's tastes.

And I'd love to do the grocery store monetization idea, but trying to form partnerships with the grocery chains always seemed like a daunting time commitment. Maybe I'll send out some feelers this week.