[Flakbadger]

Without having read most of the comments, and knowing that someone has probably already put it more eloquently than I can, here is my $.02 ($.029 if you're from Canada).

Hypermiling has made me a safer driver. I have never paid more attention to my mirrors in my life.

While I have always tried to be a safe driver (8 years, no accidents yet) I strive to hypermile without overly inconveniencing other drivers, and that means staying in the right lane and being aware of what's going on around me.
I frequently "pass myself for others" on the freeway, switching to the center lane when some dumb-ass inevitably tailgates me in the right lane while two other lanes are completely open, and try to watch traffic far ahead and behind me, to better anticipate my driving.

So while "extreme" hypermiling (prolonged P&G and EOC) might appear to the casual observer as a more dangerous way of driving, my own experiences tell me that it's probably the exact opposite, and drivers engaging in this are likely safer than those around them.

~Matt