Yesterday an 18-year-old journalism student told me he’d deleted his entire Twitter history using TweetDelete. The same day I noticed that another had changed his Twitter username to remove a reference to Newcastle United.

I was not an innocent bystander – I have to admit: I’d sort of advised them to do this…

Full circle in five years

Some history: I’ve been training journalists and student journalists to use Twitter for almost five years now, and have seen an enormous shift in that time.

In those early classes – between 2008 and 2010 – the difficulty was getting people to write more informally: almost no one had a Twitter account, so they approached it as a professional tool, with professionalism very much in mind.

By the third year, however, things were starting to change. By then around half would typically have pre-existing Twitter accounts, and many were using them in a personal capacity. The problem was not using Twitter in the first place, but how to combine the professional with the personal. “Should I have a different account for personal use?” Yes, I used to say.

Now I don’t.

There’s no such thing as a personal Twitter account

I no longer suggest having separate professional and personal accounts because, aside from the difficulty of running two accounts, frankly there is no such thing as a truly personal, even private, account if you are a journalist.

Some manage the balance: Joanna Geary, who maintains @guardianJoanna and @joannaGeary, springs to mind. But Joanna is able to do that because her ‘personal’ account is barely distinguishable from her ‘work’ account: she acts professionally; she talks about things that interest many of the same people who follow her ‘professionally’.

Joanna, in other words, is the exception.

In the movement from one audience (close friends) to another (strangers who may be judging our credibility as reporters) the harsh truth is that we will be judged unfairly against a standard we never anticipated.

And so I ended up showing TweetDelete to a class of 18-year-olds.

And I only had to mention SnapChat, and sexting for them to get it.

Welcome to the world of permanence. Please keep an eye on your past. For the sake of convenience, you may want to delete it (at least TweetDelete will give you an archived copy).

Note: Ross Hawkes has a fascinating exercise on the same subject: he will find tweets by members of the class and present them back to the class with the name removed. What would they think? “But it’s out of context!” Exactly.

Related: Why you might not ever get a job again… if you swear a lot on the internet