I love some of the rationales for not doing continuations on the JVM. Like this, from LtU:
There are a variety of reasons why we haven’t implemented continuations in the JVM. High on the list: continuations are costly to implement, and they might reek havoc with Java SE security model. These arguments are pragmatic and a tad unsatisfying. If a feature is really important, shouldn’t we just bite the bullet?
I just had that conversation with a friend before he left for JavaOne. He's frustrated by a number of things in Java, which all go back to the needs of the security model - his point being that it has less relevance for a server side application. I'm running this application on a Smalltalk server, where arbitrary code could be loaded in at any time. Here's the catch though - only two people have permissions on the system. So in order to mount such a code loading attack, one of the two of us would have to do it. Hmm - seems unlikely.
Anyway, that led me to Tim Bray's post:
This notion, that the Web GUI is insufficiently interactive and we need something richer, is widely held among developers and almost never among actual users of computers, and it’s entirely wrong. I can remember when people were forced to use compiled Windows and X11 applications, and most of them were extremely bad because it’s really hard to design a good interactive UI; when the Web came along, more or less everyone abandoned those UIs in favor of the Web, almost instantly and with shrieks of glee.
I'm calling BS on that. I'm not sure which user base Tim has met that generated that reaction, but either it was an oddball bunch, or the client applications they had to start with sucked. A lot. I deal with sales staff all the time, and they absolutely despise the web based sales tools that have been forced on them. Heck, most of them still use ACT! (or something similar) for their own use, and use the web system as little as they can. In customer visits, I get the same kind of reactions from people about the web apps they've had rammed down their throats.
Here's the thing: web apps aren't useless, and in the right place they solve problems very well. However, no one should be deluded into thinking that this is being done "for the user" - it's being done for IT, which hates having to manage client system deployments across a diverse range of hardware and software. That's not an unreasonable reaction by IT, but no one should confuse the desires of IT with the desires of end users.