RSA 2015 Facebook, Google and Microsoft spent a few minutes today discussing at this year's RSA conference in San Francisco how they attempt to protect your privacy.

El Reg asked execs present from the trio of tech giants to name their biggest privacy cockups, and surprisingly two out of the three had an answer.

"Beacon might be a good example of this, although it was before my time," said Erin Egan, chief privacy officer at Facebook.

"It was really interesting to get people to connect and share about what they are purchasing, but it had ramifications. People were surprised by it – I didn’t know that I was sharing what I bought with my friends. What we've done now is bifurcating what's going to an app ... so users understand can censor it."

Facebook launched Beacon in 2007 as a system for sharing with friends what purchases had been mode on websites that supported the system, and immediately kicked off a firestorm of protests when people realized that the "news" that the jumbo tub of bacon-flavored anal lubricant you'd just purchased would be broadcast to friends and family.

The Beacon system, while undoubtedly a money-spinning idea, sparked off a series of lawsuits against Facebook and store chains, and the system was dropped in 2009. Facebook CEO Mark Zuckerberg wrote a public mea culpa after the incident, and promised to learn from his mistakes.

Back to RSA, and Keith Enright, director of Google's privacy legal team, acknowledged that Google Glass could be an example of where the Chocolate Factory had got things wrong. Within Google, he said, Glass was seen as a logical next step in technology, and the ad giant underestimated quite how uncomfortable the techno-goggles would make people, despite taking precautions.

Google decided very early on not to allow facial recognition software to be used with Glass; a decision, Enright said, came after feedback from focus groups.

The case for Glass wasn't helped by some high-profile snafus. One bar in San Francisco banned customers wearing the camera-fitted spectacles, even before they had gone on general release (it later admitted the ban was a publicity stunt) and then there was Sarah Slocum.

Slocum claimed that she had been assaulted in a "hate crime" while wearing the glasses in an SF pub. The video she shot, however, showed that she wandered around notorious dive bar Molotov's half an hour before closing time filming people before one of them took offense.

As for Microsoft's biggest privacy mistake, we'll never know. The moderator moved on before Redmond's chief privacy officer Brendon Lynch could reply. Maybe readers have suggestions they can post in our forums. ®