Why Let Grandparents Rule?

I have been vacationing at my parents house for a week or so, which is why I have not posted a blog (jen), but have realized while I've been here that it does not matter what I do or say to my parents about the way I discipline my children, because it goes in one ear and out the other! I understand that grandparents are supposed to "spoil" their grandkids - I get it, really, but I don't necessarily agree with it one hundred percent. There are some things that I won't get crazy over, but not disciplining my children is unacceptable... chocolate for breakfast I can get over. So, do we as parents say something to our parents or do we let it slide because it's not every day our kids see their grandparents?