correct and incorrect uses of canvas

hi all,

Accepting that text editing in canvas is not a good idea and buidling
traditional complex UIs in canvas is not a good idea.

Is the use of interactivity in canvas appropriate in any circumstance?

For example are the following correct or incorrect uses of canvas?

interactive graph
http://thejit.org/static/v20/Jit/Examples/ForceDirected/example1.html

drag and drop, resizable objects
http://kangax.github.com/fabric.js/demos/customization/index.html

UI Dial With Snaps
http://bocoup.com/processing-js/docs/?page=UI%20Dial%20with%20Snaps

Visual Knowledge Browser
http://askken.heroku.com/

Handling Click Events On Chart
http://www.deensoft.com/lab/protochart/clickevent.php

drag and drop
http://easeljs.com/examples/dragAndDrop.html

Sumon WebGL (2d canvas animation fallback)
http://labs.hyperandroid.com/sumon-webgl

Sunburst of a Directory Tree
http://thejit.org/static/v20/Jit/Examples/Sunburst/example2.html

letter pair analysis
http://www.m-i-b.com.ar/letters/en/

If  the above are not considered misuses of canvas, does the current canvas
2d spec provide the means to expose the required information to make the
above accessible to users of AT?

If they are misuses of canvas how can we convince developers not to use
canvas in these ways?


regards
Stevef