Yes, event.altKey would seem a better choice as it maps to Alt on Windows and Option on the Mac. Not sure about Chromebooks (which don't even have any modifier keys other than Shift) or Linux though. Or mobile browsers.
Two more issues: http://i.imgur.com/uBpTr0m.png - somehow managed to get two links superimposed ("meteor" and "j"), and moving blocks of links took a rather long time.
I like this notion of the desktop metaphor being extended to bookmarks. Actually I was quite disappointed to see that Google missed this trick with their new Chromebooks, preferring to stuff app links into a bar at the bottom of their desktop. Your approach makes a lot more sense.
Quick bug report, there is a display issue when one's browser window (or screen) isn't wide enough, it chops off whatever is meant to be at the right hand side at the top: http://i.imgur.com/GfNtJcv.png
Another issue is that sub-memorypools with identical names can be created. Not sure if that is intentional or not.
Also a suggestion, I think that dragging a bookmark icon on top of a memorypool icon should move it into there.
