People can tell some attention-grabbing stories on Facebook, the social-networking website. It is easy for distant onlookers to feel that they missed out on all the fun. But only those who were in the room at the time know whether what happened was all that exciting.

The same caution should apply to Wednesday’s announcement that Microsoft had taken a stake in Facebook – one which implied a valuation of $15bn. Only the in-crowd knows what Microsoft got for its $240m: a tiny equity stake, yes, and the expansion of a pre-existing deal to broker exclusive banner advertising. But other investors seem to be willing to buy equity on a similar basis.