I've had a recruitment consultant suggest I use a gmail e-mail address on my CV, because it looks weird to have an address at a domain (my own, and not anything strange btw) that people haven't heard of. Sounds crazy. But try dictating an e-mail address over the phone to a hotel or whatever and see that if you say 'Fred Bloggs seventy six at gmail dot com' or whatever, you never have to repeat yourself, whereas anything less usual you'll be spelling it out all day.
On the technical side, one hears about individuals' domains being marked (blamelessly) as possible-spammers by the big e-mail services, and finding it hard to get messages through. There is effectively some scarcity in legible, desirable gmail addresses.
I agree that it's not black-and-white. It's also not as dramatic as the land analogy suggests. There are plenty of other email providers that are perfectly socially acceptable to use.
Counter point, I’ve been told by recruiting that my email makes me stand out because it’s not the norm domain name and it’s a little “fun” in the sense that it conveys a little light personality.
I'm 100% certain that a number of opportunities I've been offered have been because I proved a certain level of competence by maintaining my own email and domain; this certainty is largely due to the incidence of comments like the ones you note. It's definitely a way to stand out.
