As a commuter who rides the train that feeds Fenway, I can say that's a major detriment. Nothing like 30 minutes in a packed train with sweaty drunk fans to end your day in the office 2-3 times a week.
The more interesting property relates to subscription. Like RSS, you start receiving updates from contacts you've explicitly selected. Spam-proof, and highly conducive to emergent conversations. (If you're a Facebook user, this is kind of like the News Feed.)
Here's another way to look at it: logging into your microblog is like joining an enormous IRC channel spanning the entire world, only almost everyone is set to
thats why we see more and more im systems develop a system of offline messages. [...] only thing missing really is a way to save and sort individual messages like one can mail, and upload files in a similar way to how one can do attachments to a mail.
Um.
At this point, haven't you essentially reinvented the email wheel?
I don't see how this hypothetical system is substantially different from email. Well, to be fair, "email plus presence" (see: tightly integrated email/IM systems like Gmail/Gtalk or Mail.app/iChat).
Note also that whatever it is about email that "the kids" don't like anymore, they'll also grow to dislike about "IM plus offline messages plus mailboxes plus attachments".
Care to cite a source? It was my understanding that it in fact took a considerable force to bring a plane down, unless you happened to detonate inside the cockpit. Cabin decompression would at best kill a couple passengers and force an emergency landing.
And while a plane can be used as a weapon more easily than a train, I don't see how liquids would be the controlling factor in such a takeover.
Function reject.