My mum "blessed" me with 2 middle names - Ann and Louise. Not long after she passed away my OH and I were told we would not be able to have a baby without IVF and decided we didn't want to go through that, so I changed my middle name to Gloria, after my mum instead of having a child and naming it after her. I think middle names are a handy way of squeezing parents/grandparents names into a child's name without having to actually name the child after them.
We've changed our minds about the IVF and decided to go for it after all, i was only saying earlier that i like the name Parker as a girl's name, and we could give it the middle names Edith and Evelyn after our grandmas, but now i realise that the child's initials would be PEED, which is perhaps not such a good idea...