A Google Groups thread suggests that Google should not only show the URL, the type of error and the date of the error in the web crawl error report within Google Sitemaps. It should also referrer data, so that the webmaster can better diagnose the issue. That will tell the webmaster the source of the error and be able to better resolve the issue.
Adam Lasnik who is currently on a roll, answering questions this morning, wrote;
we've indeed heard this request before, and so it's definitely on the Webmaster Tools folks' radar!
Good to hear, I wonder how soon it will come?
Forum discussion at Google Groups.