What are the proper bounds of reporting versus interpretation in writing history?

In a recent blog post, you criticized "interpretation-heavy" histories. (http://www.philosophyinaction.com/blog/?p=9611) What constitutes too much or otherwise inappropriate interpretation -- and why? Does interpretation by the author impair the reader's capacity to draw his own conclusions? Doesn't an author's mere selection of which journalistic details to include in a history constitute an implicit interpretation?