Look at this coupon for "20% off ink" from Staples (UPC code omitted):
Now read what it says: "Excludes all toner, Epson® ink and toner, HP ink and toner..." What the heck, Staples? The last printer I bought from you was an HP printer and now you going to require that I pay full price for ink for it? When HP will sell it to me for a discount? Why do I even do business with you when you do a "bait and switch" on me like this and waste my time?
I unsubscribed to further emails from Staples. I sent a message to my Staples representative and it bounced with this notice: "Your message couldn't be delivered to the recipient because you don't have permission to send to it." (sic)
The next time I need office supplies, I'll check around and try to find someone with everyday low prices, not a company that keeps sending coupons that don't apply to me anyway.
Update June 29, 2016: "Your message couldn't be delivered to the recipient because you don't have permission to send to it." is a Microsoft Outlook euphemism for "The recipient is no longer with the company."