Give thanks you’re not the PR or social media pro behind this failed campaign.

On Tuesday, Australian supermarket Coles tweeted:

“Finish this sentence: In my house it’s a crime not to buy _______”

You can probably see where this goes. Here’s a sample of the replies (unedited):

• “Not buy coles brand products because of the benifits of no added msg and no artificial colours.”
• “Fruit & veg from a place that pays their farmers fair prices & sells seasonal produce not stored in a freezer or artificially ripened.”
• “BREAD AND MILK AT PRICES THAT ALLOW PRIMARY PRODUCERS TO SURVIVE.”

Coles recognized its error, tweeting the same day: “It's a social media crime not to ... finish a sentence yourself. Sorry guys that post was not meant for Twitter!”

Judging by the Coles Facebook page—which features a handful of questions such as, “What are your favourite products at Coles online that make your life easier?—it seems that post was meant for its Facebook wall.

Last year, another Australian company, Qantas Airlines, committed a similar blunder when it launched a promotion asking Twitter members: “What is your dream luxury inflight experience? (Be creative!) Answer must include #QantasLuxury …” Thing is, Qantas was involved in a labor dispute at the time, which meant the #QantasLuxury hashtag was overrun with negative comments.

Other brands have experienced similar Twitter-born PR headaches thanks to hashtags and poorly planned promotions, including McDonald’s, Sports Illustrated, Research in Motion, and Toyota.