I discovered scratches in the oleophobic coating this morning and was rather bummed about it. Like everyone else, I've babied my phone and it's been in a Spigen Slim Armor or Ultra Hybrid the entire time. I suspect that having to partially put pressure on the lens to remove the Ultra Hybrid was the culprit.
I used a couple paper towels with moderate pressure, soaked in 91% rubbing alcohol, followed up with a microfiber.
As others have had same results with a qtip and toothpaste, I'd probably recommend going that route, as there's less pressing involved (which was scary).
Oddly enough, the front facing camera had the same issue, however rather than scratches, most of the coating was just flat out gone.
As for a lens protector, until someone makes a glass one, I'm not interested.
HTC One M8 Gunmetal
AT&T, Sunshine S-Off, ARHD 10.2, TWRP 2.7.1, ElementalX 1.01, undervolted
Other devices: Chromecast | iPad Mini 16gb, black, iOS 7.0.6 jailbroken | iPad, 16gb, iOS 5.0.3 jailbroken | Apple TV 2 | HTC Liberty, CM10
iPhone 5S (x3), jailbroken | HTC One M7 Silver, S-Off, ARHD | iPhone 4S, jailbroken | iPhone 4, jailbroken | iPhone 3G, jailbroken | HTC Mogul