Justin Bieber lost 3.5m Instagram followers last Thursday. No, not because of some spectacularly ill-advised photograph of him kicking a kitten. Bieber was the most high-profile sufferer of Instagram’s crackdown on inactive and spam accounts, although given that post-crackdown he still had 20.3m followers, we suspect his social media team won’t be weeping too hard. But the changes did see Bieber fall behind Kim Kardashian for overall followers: she only lost 1.3m on Thursday, leaving her with 22.2m. “We believe this will provide a more authentic experience and genuinely reflect people who are actually engaging with each other’s content,” explained Instagram. And in separate news, Citigroup has upped its valuation of Instagram to $35bn. Which, if you remember, is 35 times the $1bn Facebook agreed to pay for the company in April 2012 (and, if you’re an even better rememberer, 49 times what Facebook actually paid for Instagram, since quite a lot of it was in shares and their value dropped).