A possible example site that may have sufficient copy-blocking is snopes.com. You cannot simply select the text of a snopes report by dragging. You can, of course, get at the underlying html -- and thus the text itself -- by a number of methods. As there are both "Print this" and "Email this" buttons on the page, however, the casual visitor thwarted in a simple copy operation will likely take one of these routes to obtain a copy, thereby providing the snopes folks some information on the way.
So, how do they do this?
var omitformtags=["input", "textarea", "select"]
if (typeof document.onselectstart!="undefined")
document.onselectstart=new Function ("return false")