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.

That strikes me as very reasonable. 20% (15%, whatever) time is largely self indulgent plus self education. I have no problems with being expected to supply that initiative. I've done it before, and invented products that the company ended up selling (until I realized the only payoff in this case was a "we'll compensate you for this later, trust us" - I'm not talking about any company discussed here, btw).

This way it is not goof-off time as it will not attract anyone except self-starters and thinkers, but the company is providing intellectual and material resources. You get to have fun, rejuvenate yourself on the job, the company contributes some, and maybe, just maybe, you hit the jackpot at some point. If not, well, you learned some stuff and had fun.