Sure, anything can be built given enough time :) The difference is that those modes can be built in a couple of hours with arbitrary UI and virtually any interactions you can think of. It's hard for me to imagine being able to build any of the things I showed in say Eclipse in any reasonable amount of time.
The idea is that Light Table will be built from the ground up to support very dynamic environmental contexts in which you can place anything.
But, instead compare that to Emacs, these are exactly the sorts of things people can and do do in emacs in reasonable amounts of time. And exactly why emacs has many great tools, from paredit-mode to SLIME.
The comparison to emacs isn't meant as a slight to LightTable either, but please, let's not forgot the past when creating the future.
I've seen a lot of cool stuff in Emacs, but I haven't seen anything nearly this nice done in any reasonable amount of time. Emacs is a predominately text-based thing. Light table is not.
With that said, wouldn't his "It's hard for me to imagine being able to build anything I showed in say Eclipse in any reasonable amount of time" comment also apply to Emacs?
Generally speaking, it ends up much less graphical, which is the major failing of Emacs in comparison to Lights Table, but if the functionality is what you are looking for, instead of the pretties then Emacs has similar development time. I'm not saying there is no value in Lights Table, but we should just be clear on exactly what the advantages are.
The idea is that Light Table will be built from the ground up to support very dynamic environmental contexts in which you can place anything.