deflepper - 10:59 am on Aug 26, 2013 (gmt 0)
Another possible explanation is that the long and unnatural keywords come from sites that participate in adwords's search partners network.
For some of these sites, google doesn't report the queries made by users but a string of keywords taken from the navigation or filepath of the page on which the adsense ads were shown.
For instance a keyword like "category brandA brandA widgetA sale" could come from a url like /category-brandA/brandA-widgetA/sale.
I haven't seen this for natural language looking types of queries but it's not unthinkable.