Of course it's marketing gimmick. After all, hydrophobic coating has been around and used on most ophthalmic lenses and many sunglasses (ie MJ) for years. BUT you gotta give Oakley credit for their marketing skills, as they make it seem like they invented the concept and I've never seen this and other lens characteristics (ie polarization & impact resistance) presented better anywhere else.
All marketing stuff is biased as you can see from this video (sure to get your blood boiling):
http://youtube.com/watch?v=2mbDokgXmFA