If you sell online and your web page says you ship daily, don't mail a package a week after the order is placed and paid! Good grief! I would think this is common sense.
I am appalled at some sellers (large and small) who just ignore the customer after payment. It's very easy to use the PayPal or UPS shipping that automatically sends the buyer an email when the mailing label is created. It includes the tracking number and a link to see the package's status.
I hope this is common sense to all of you and you know I'm not ranting at any of you!