London Luton airport apologised today after a "new, over-enthusiastic member" of its staff posted an image of a plane crash to the company's Facebook page.

The caption read: "Because we are such a super airport...this is what we prevent you from when it snows...Weeeee :)". Although some people might be able to see that the staff member was trying to bring some light-heartedness to a formal corporate Facebook page, not everyone got the joke. Especially when it transpired that the image was of a plane crash at another airport, where a child on the runway had been killed. It's unlikely that the staff member had considered the ramifications of posting the image, or even knew about the story behind the picture, but does that excuse the act? No.

When posting on social media, people often fail to acknowledge the tiny but very important difference between the things you think inside your head and the things you think and then say and then share with millions of other people, which happens outside your head. The crucial difference is that other people can’t see inside your head, at least not yet. (Yes, Google, I mean you and your suspicious Glass goggles). Inside your head is the place for the bizarre, idiotic and dark thoughts like, 'as I spend all day glued to my desk, would my co-workers notice if I removed my trousers once I got to work?' Inside is safe. Outside has consequences.

We all have bizarre, lurid and downright horrible thoughts from time-to-time, and they are OK to share with people that know and understand you (and your crazy little brain) but not with the world at large.

Whether we like it or not, thoughts shared online carry further and more quickly than they ever have in the past. Remember last Remembrance Day? 19-year-old Linford House posted an image of a burning poppy on Facebook which quickly spread beyond his own circle of friends. Whether his intended message – that the marketing around poppy day had gone too far – was right or wrong, the upshot of it was that it was upsetting to veterans and war widows, who House was made to meet face-to-face as part of his sentence. The message here is clear, if you are thinking about something inside your head, consider the people it will affect before you put it out there. It’s very, very hard to take back once the damage is done.