OK - my 1st post. But here's my experience on 10/31/08 to add to the mix.
Went to OKC, Belle Isle Walmart.
Had mixture of coupons - 8 were internet and complied with Walmart's guidelines for those type of coupons.
Was carrying copy of their policy in my folder - have not had to EVER use it in these 8+ months of doing internet coupons.
3 cashiers, 2 csms - each agreed with the other - no internet coupons.
I told them I would return the items the coupons represented at Customer Service.
Asked for a little space to unload bags and sort.
After 45 minutes of sorting, waiting in line, etc., I got a refund of almost $20 on those items.
(It was the principle of the thing - I was NOT going to pay full price! Had worked hard to organize had budget for this trip!)
Called the store manager, Dawn W., when I got home.
She was unable to access the coupon policy - slow computer.
Still assured me this wouldn't happen again.
I asked what I should do next time.
She said the CSMs would go over the coupon policy with cashiers in 1X/week meeting.
What I learned:
Make sure your Walmart coupon policy has a recent date on it. One CSM implied my 1/2 sheet of printed policy indicated I had deliberately torn off the bottom to not disclose the date.

Make sure you know the store manager and use their name when there's a question.
Following the rules doesn't always mean a thing!