I was in my local supermarket Mon and Wed this week. Between that time I noticed several products I usually get go up in price 20-30 cents. I like the idea and will have to get some post-its.
I live alone (well except for my dog) and hate shopping, so I tend to go to the grocery store on a monthly basis, load up on lots of non-perishables, and freeze anything that won't last for more than a week or so. Because I go so infrequently, I tend to notice incremental increases a lot more than I'd imagine somebody who goes every week or every two weeks.
So far, this year I've been stunned by the increases just about every time I've gone to the grocery store.