mbostock/d3 — pull request #597 by mmeisel (2012-03-20 18:57:45+00:00)
Title: In d3.behavior.drag, the initial mousedown event should be cancelled

If you don't call preventDefault() on the mousedown event, the browser will select text on the page while you drag. For example, try dragging the circle over the text in this fiddle:
http://jsfiddle.net/M8uga/

This event was being cancelled in the previous version of d3.behavior.drag (before the rewrite), so I'm guessing it was just an oversight.