Recently I have begun exclusively shooting on Blackmagic cameras so that I can make color matching a gosh darn breeze! I used to shoot across multiple different types of cameras including H.264s and back then I was always told to shoot in 23.98 or 29.97 to keep it all straight because of the old canon dslrs. However, now that I've moved to Blackmagic, I'm curious if I should lock them all at 30fps now that they are all using same codecs and manufacturers and any reason why I would NOT want to do this.
29.97 and 23.976 are broadcast standards, called "drop-frame timecode." If you want to shoot true 30p video with a Blackmagic camera, I think you're fine to do so as long as your output is just for the web and you won't mix in footage from other camera/recording systems.
Editing systems now can handle mixed formats quite well, but still there can be problems and mixing drop-frame and non-drop footage could give you a serious sync issue of sound and picture.
BM camera are one of the few camera systems to offer a true 30p option, most are 29.97p as it is close enough and it is the broadcast standard.
RadioU TV & Animal Basement
14 years experience as a fulltime broadcast shooter, editor & broadcast designer.