> When was the last time an entire category of jobs became obsolete fast enough that laid off employees blamed the technology?

Containerized shipping. Interestingly, it's in the world of logistics too. Longshoremen/dockworkers/stevedores used to be among the most common occupations in the US at the turn of the century, but now the industry employs a tiny fraction. A small group of a few hundred people can effectively run an enormous port like Oakland's.

Yes, the employees blamed the technology, but so did local governments. Places like Baltimore relied pretty heavily on the docks to supply their population with jobs; when those disappeared quickly many cities (especially on the eastern US coast) had a really tough time economically.