Upon presenting a coupon, via my mobile phone, for 10% off any purchase, the old lady behind the counter immediately said "No, no, no, no!". I was told it was a mistake on the coupon service's part. MP Liquors (located next to Giant on Baltimore Nat'l Pike) did not offer to honor the coupon as a good will gesture (it's not my fault there was an "error"), nor did the old, crabby lady say "sorry" or even "thank you" for my $58 purchase. So, they've lost of regular customer over less than $6. There are plenty of places to buy booze.