IT TOOK a while to join the dots. On the morning of September 13th owners of several types of HP OfficeJet, a printer designed for the home and for smaller offices that is manufactured by HP Inc, an American seller of printers and computers, switched on their machines and found them not quite the same. The night before they had been able to print with any sort of ink cartridge. Since that day only machines containing original HP cartridges have churned out copies. The cause, enraged customers came to realise, was the deployment by HP of a firmware update that blocks rival ink.

HP had reason to act as it did. Though its printers business remains profitable, revenues fell by 14% in the year to July. More-paperless offices take most of the blame: printer shipments have tumbled by a fifth since 2007. But rivals in the market for ink squeeze margins. Non-original cartridges now make up about 26% of the trade in Europe, the Middle East and Africa, and 16% in North America.

Dirt-cheap “clone” cartridges, mostly from China, have spread over the past decade. HP’s move obstructs fakes, which do break copyright law (and the odd printer). Also affected are lawful...Continue reading