Firstly to say I am not arguing against what you said. I do however want to add to point 4.
Getting employee buy-in is important. An employee that is engaged, that believes he has a higher purpose than just working for this company will put more effort and pride into his work. In theory higher quality and more work is the result.
This internal marketing helps employee retention as well as getting many of them to do more for no additional pay because they are committed and feel it is their duty.
Most new employees will eat this up and feel they are part of a larger group, a wider family, with a purpose beyond just plain old Monday work. After a period of time people, being smart, wisen up and read between the lines if they have not already. then the "engagement" becomes a game of pretending. Managers pretend to be engaged and pursue engagement activities (that include making sure no one works from home) and employees pretend to be engage and embrace the "culture" as a valued framework.
Many companies will cite Yahoo's experience and many managers will see it as "proof" of something. I believe it all boils down to the employee in question.
Most employees will be very concerned that they may be viewed as not doing much if they are working from home and will often do more "just to make sure". but perception is the name of the game. If your manager thinks people that wear jeans are not serious about work well...we know what happens if a candidate shows up to an interview in jeans.
As a society we are still a bit far off the holy grail of working from home. The old way of thinking is still prevalent and despite having the technology this way of thinking is holding us back as a society. Imagine the cost savings if you did not have to provide your employees with environmentally controlled facilities and giant office spaces. Imagine how much traffic will be saved if 50% of us do not have to actually be physically at work.
Personally I find working from home easier. I can sleep more and have an environment that I enjoy and helps me concentrate. I don't need a manager to interrupt me as he reads through his emails or colleagues playing music wanting to gossip over coffee or deal with the less than gourmet food on offer.
In conclusion I think that a person wanting to work from home needs to find the right employer and that is where the real challenge lies. Most do not advertise that you can work from home so it's still a matter of finding out manually. It's one of the questions I'd ask of a future employer.