Runs4Sanity
http://running.competitor.com/2014/07/news/grand-canyon_108186
It sure sounds like these guys are determined to ban runners completely, wonder how often you come across a ranger or any other authority figure in the canyon? And I am pretty sure runners aren't the only ones leaving trash and being rude... but I have never been there (yet) so you more experienced runners can let me know.
*Do It For Yourself, Do It Because They Said It Was Impossible, Do It Because They Said You Were Incapable*
PRs
5k - 24:15 (7:49 min/mile pace)
10k - 51:47 (8:16 min/mile pace)
15k -1:18:09 (8:24 min/mile pace)
13.1 - 1:53:12 (8:39 min/mile pace)
26:2 - 4:14:55 (9:44 min/mile)
As the canyon is a relatively "high use" area, you'll probably see or run into a couple rangers on your way down & back up ... they are there to ensure the safety of all of the canyon visitors. People tend to bite off more than they can chew & the rangers are there to <hopefully> nip that in the bud before things go awry.
I definitely agree on their concern for the not so equipped runners/hikers but I sure hope that doesn't ruin it for those of us who haven't been yet, but I don't think I would go just to run the R2R2R, but just to enjoy the trails.