In the next several years, it might be weird to _still_ have a Facebook account. Just like an AOL email, myspace account...
I left FB in 2009 and haven't looked back.
Needless to say, there's a convergence appearing, and the distinction between desktop and mobile may virtually disappear in time. Your efficiency arguments make logical sense from a techie perspective but are not necessarily pragmatic for the broader population. I think your analysis is much more in line with the present and past, but not really a vision of the future. In fact, the suggestion that desktops will "always be the best value and experience at home" comes off to me as rather myopic.
As the parent reply suggested, your piece is very close to satire. You are blinded by your own workflow and think that people 'tire of 15" ' laptop screens and such. But that's just you projecting your own preferences on the broader public, and it's exactly the kind of thinking that stifles creativity. I realize I'm coming off a bit harsh here - but it's clear from your posts that you are thinking in a bubble.