I remember sitting in the London Coliseum one wet Friday night back in 2009, waiting for the curtain to rise on Rupert Goold’s production of Turandot. When it did, the audience let out a collective gasp.

I don’t think it was because said curtain stopped abruptly a few metres into its ascent (that was probably intended, but at ENO in the noughties, you never really knew). Rather, it was prompted by what we were presented with on stage and its effectiveness as a visual counterpoint to the musical culture-shock with which Puccini rips open his opera: a Chinese restaurant so gaudy, so foreign and yet so close-to-home on St Martin’s Lane that it packed an instantaneous dramatic punch. Whatever you thought of Goold’s production – and I was one of the few journalists present who thought it pretty successful – it was some way to open a show and set out a conceptual stall.

Fast forward nearly a decade, and a few weeks ago I found myself at the old opera house in Copenhagen, waiting for the curtain to rise on Lulu. Not Alban Berg’s expressionist masterpiece, but Friedrich Kuhlau’s 1824 singspiel based on the same story as Mozart’s The Magic Flute. The piece hasn’t been staged for 180 years, so I had little idea what to expect. But when the curtain rose to reveal an equally striking scene to that which had opened Goold’s Turandot – a stage almost entirely covered with grass and reeds, upon which carefree nymphs were playing a decorous game of badminton – my reaction was not one of surprised delight as it should have been. Instead, I got the funny feeling I’d seen the whole thing somewhere else before.

And I had. Where? On Instagram, naturally. The production by Christian von Götz was a good one, full of clarity and wit and with wickedly inventive costumes courtesy of Sarah Mittenbühler. But for each little scenic revelation – the grass, the smoke effects, the chorus of monsters, the very particular way in which the hunchbacked reprobate Barca had been imagined – Instagram had got there first.

That’s my own stupid fault for following the Royal Danish Opera on Instagram, you may say. A valid point. But hundreds of others follow that account too. The current social media landscape prompts us to click ‘follow’ at the sight of a known institution with hardly a second thought as to what we might see and what spoilers we might encounter. Back in January, when I logged on to Instagram, I was presented with detailed set shots from the company’s new, rehearsing production of Il Barbiere di Siviglia, ‘inspired by the world of 1930s black and white movies’ according to the captions. By the time I came to see the actual show, I’d seen every last black and white hairbrush, inkwell and wrought-iron light fitting at close quarters.

Does this ruin the magic of the performance, the surprise of what’s in store? That’s for each of us to decide. I applaud the social media teams at opera houses who do so much to create a buzz around a production’s opening (and to maintain the same excitement throughout the run). It’s fair to assume that only die-hard fans are engaged with the relevant opera companies on social media anyway – the sort who relish the chance to get a sneak peak of forthcoming productions.

But there are elements of the trend that are more concerning. It doesn’t take Mark Zuckerberg to recognise that today’s social media trend often becomes tomorrow’s pervasive normality. Right now, opera houses keep their followers hooked via behind-the-scenes realism that lets you in on how things on stage are done – makeup, special effects, vocal and dramatic preparation from the cast and so on. Of course, the social media monster insists that you titillate your followers with a steady stream of micro-revelations. But quite apart from sucking elements of magic and surprise from performances – whose incarnations are alluringly mysterious by their very nature – the steady stream’s growth into a full-on waterfall could throw up a more serious problem. Audiences might become so familiar with the look of a production that they feel they’ve seen enough, without bothering to buy a ticket at all.