Correction.
Some people, work their assess off all times of the day because now they can be reached around the clock. Some people work the same but make up with availability which can be valuable in itself (I am one of these people). And some people goof off even more than before.
Maybe the total productivity didn't change, but definitely it has shifted.
The question is what happens now. I think what happens is companies will get better at understanding who is and who isn't spending time working (I am careful not to use word "productive"). And some companies will monitor this and some will make conscious decision to focus on trying to get better at understanding actual productivity.
The ones that monitor working time I call sweatshops and I would try to stay away from at all cost. You want to compete on quality of your work or even on productivity. But you definitely do not want to compete with your coworkers over who can spend more time by the computer because there simply are no winners in this game.
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One way it can bite people is that it may help the companies identify who is productive (if the company is smart about it).
I once talked with my boss about why he is allowing employees to access company funds (within certain limit). The finances people are furious and want to cut it off and instead give some ridiculously low limit for spending.
So one argument is that it allows people to be more efficient. When they need something, they don't have to wait for approvals or for "process".
But then the boss also says: "It is much cheaper for me to have an employee steal couple thousand dollars from me because I can easily identify it and fire the employee. It is much more expensive to keep that employee."
I think the same applies to working from home. When you allow people to do pretty much what they want, thinking they are unsupervised, you have now much better chance to identify employees who are completely immature, irresponsible or fraudulent about it.