I went to Shoppers today to use $1 off Butterball turkey bacon, ($2.59) and they said they don't take IP past 99 cents! I was so annoyed!
I emailed corporate and they sent a response:

Thank you for taking the time to contact Shoppers food & Pharmacy. Unfortunately due to an increased number of fraudulent Internet coupons in the marketplace, Shoppers Food & Pharmacy no longer accepts Internet coupons for FREE items. At this time we are still accepting Internet coupons for CENTS OFF (up to .99). We realize that many customers receive these coupons over the Internet and believe they are legitimate. Unfortunately, in many instances they are not. Also, the manufacturers have told us that they won't reimburse retailers for them if we do accept them.

I really liked getting IP and am really bummed out.