Google’s “20% time,” which brought you Gmail and AdSense, is now as good as dead

"if 20% time has been abandoned at Google, are other companies, which reportedly include Apple, LinkedIn, 3M and a host of others, wise to continue trying to copy it?"

That's incorrect, AFAIK 3M were the first company to pioneer this approach (with 15% of time spent on self-directed projects).

For example see: http://www.fastcodesign.com/1663137/how-3m-gave-everyone-day...

Talking to a friend at 3M (who has been there 20+ years, an engineer with dozens of patents) I am told that while 15% officially still exists, for a long time it's effectively meant working 115% of hours.

Nonetheless the tradition allowing self-directed research continues at 3M - and this might mean using lab resources, or creating prototypes without getting approval.

> Nonetheless the tradition allowing self-directed research continues at 3M - and this might mean using lab resources, or creating prototypes without getting approval.

And get hours paid for it, even it being extra hours you wouldn't do other way.

"And get hours paid for it,"

I don't work there, but I feel pretty safe in saying 3M researchers are not hourly employees.