Software glitches, bugs, etc call them what you want. People can downplay them as minor or escalate them to major/critical. But when a critical one hits production, expect a storm coming in for your company.
Critical bug are among those dreaded by CEOs, project managers and other executives. It can break reputation. It can cost companies millions of dollars. Here are the most embarrassing bugs encountered so far:

Bad Nest

In January 2016, the smart thermostat by Nest encountered a serious bug. Nest was an IOT company backed by Google.
People could not adjust their thermostats. Imagine people could not control their water heater and room temperature. The bad thing about it was that it happened during the coldest weekend so far.
The bug was identified on their Dec 4.0 firmware update. The update was rolled back that resolved 99.5 percent of its customer who reported the problem.

Divorce Gone Wrong

In the UK, the calculator that calculates the spouse’s financial worth encountered some serious error. The calculation was completely wrong and affected thousands of couple who got divorce in the 1.5 years.
The bug caused the inflation of the spouse’s finances. It took them almost a year and a half to discover this. Talk about losing not just your heart but a large sum of your bank account.
Thank You Starbucks
In April 2015, Starbucks had a major register malfunction on its stores. This affected more than 50% of its North America and Canada branches. The stores were not able to process transactions causing them to shut down the branches or give coffee for free. Talk about tough luck!

Amazon Booboo

In Dec 2014, some of the Amazon 3rd party retailers saw their wares reduced priced to 1 penny each. Because of this 1 hour shopping glitch, there were PS4, beds and matresses that were sold at super low rates. Shoppers had a field day with this glitch and bought them.

Marks and Spencer TV

Another lucky break for consumers. Marks and Spencers sold their 50 inches 3D tv from £ 1,099 to £ 199. Thats a whopping 90% off discount. They tried offering the clients a £ 25 credit but was turned down after the clients filed a petition.

Corrupted Blood Glitch at WOW

This is perhaps one of the funniest glitch in gaming history. World of Warcraft was considered a very MMORPG game in history. In Sept 2005, a glitch was released causing massive casualties to the game. A new enemy boss, Hakkar, was released. He has the ability to inflict a disease, called Corrupted Blood, upon the playing characters that would drain their life over a period of time. This disease could be passed from other players and can kill anyone who gets it. Originally it was designed to affect to the game area of Hakkar, but since players can teleport to other places the virs spread like wildfire
It was like a viral outbreak happening to the WOW cities. The bug was fixed after the event. WOW released a patch to fix it. The effects was so devastating you will laugh at the reaction of people as though the outbreak happened in real life.

Sources:
https://www.theguardian.com/money/2014/dec/14/amazon-glitch-prices-penny-repricerexpress
http://www.computerworlduk.com/galleries/infrastructure/top-10-software-failures-of-2014-3599618/
http://www.computerworlduk.com/galleries/it-business/curse-of-online-shopping-6-great-price-glitches-3594598/
http://listverse.com/2012/12/24/10-seriously-epic-computer-software-bugs/