ChrisK
En-Route
I got the feeling he meant that if you don't stick to a direct route (or whatever you file), you compromise the whole point of filing VFR, which is SAR. I'm not sure whether the search algorithm for VFR flight plans takes into account the filed route, however.
SAR takes into account the last known position combined with the route. Current methods use a 2009 NASA air search area definition study based on a statistical analysis of the location of missing aircraft compared to their intended / filed route of flight to calculate the probability of containment of an aircraft in a proposed search area. See this for way more info than you ever wanted:
http://www.uscg.mil/hq/cg5/cg534/ns...ed_Land SAR Addendum (1118111) - Bookmark.pdf
My very first exercise in class I got yelled at for not using the filed route on a VFR flight plan, so yeah, a) I've never made that mistake again, b) the instructors do a good job nailing the point home, and c) the VFR filed route is relevant =)