As several posters have already mentioned, the method of assuming a conservative mile pace, allows the runner to stray off the measured course on easy days. Avoiding the same 4 or 5 trail/road runs day after day keeps the runner from becoming obsessed with the speed they run on recovery days. Isn't it more important to run according to perceived effort on these days?
I am the first to admit that I hate doing hard workouts on anything other than a meticulously measured course or track, as I want an accurate picture of just how fast I am running. However, it's this same compulsion that often drives me to race myself even on recovery days:
"I know it's an easy day but...damn...I'm like 30 seconds off my normal pace, I'd better pick it up just a little...don't want to start running too slow."
Running "badger miles" has really helped me in my training. I may very well be running 5 miles +/- what I am writing in my log, but I'm also not tempted to push my body harder than it wants to go on easy days. In my experience, this is when injuries happen. Also, it enables me to add in soft surfaced routes that are unmeasured, such as local golf courses, unmarked trails, and parks.
For runners with a similar temperment, I think the "badger" system of mile counting is great. I am not "cheating" myself of miles in training so much as I am allowing my body to recover the way it needs to. SOme days that means 6:40 pace, other days it's more like 7:30. Every few weeks I'll jump on a track in the middle of an easy run, just to get a general idea of what my pace is, but that's it. 2 years of running this way, and I've been injury free, haven't missed a day of training.
If you really really hate the "badger" system, chill out. Remember, the track never lies, and neither does the competition in a XC race. We'll see how those crazy 7 min milers do at NCAAA's this year...(that's a joke for those of you who were about to burn me).