This wouldn’t be much of a problem on the public web since it’s pretty tough to be destructive on public web pages, but web apps, with their admin links here and there, can be considerably damaged. If you have a web app, it might be worth returning a 403 when the HTTP_X_MOZ is set to “prefetch” header is sent. This will keep Web Accelerator from clicking destructive links.
I like this "destructive links". A major point of the Web is that links are not destructive.
I think the better approach is to not use GET to modify or remove data. That's simply unnecessary and against the word and spirit of HTTP.
Remember, a link is not a widget. You can't use a simple anchor element as if it were the same as a push button. Whenever an HTML page has an anchor tag, it is explicitly advertising that the URL is safe to retrieve. By sprinkling your HTML with these landmines, it's the author that made the mistake, not the browser or web accelerator.
If you are writing web apps, it might be worth more to think about what's happening and why, rather than hack a workaround that only occasionally avoids a bug introduced by your own application. Fix the bug, and no workaround is necessary. Again - a link is not a widget.