So people are already using [ios] to talk about the iPhone/iPad operating system, which makes sense. However, as this is a security site, I imagine some people will want to talk about IOS, the Cisco router environment. Now this is Cisco's silly fault for licensing their trademarks to Apple (iPhone was one of theirs too), but what should we do about it? I think that as there aren't any IOS questions yet, we can define [cisco-ios] to be the tag for IOS and leave [ios] for iOS. But this is all very confusing...
I think this makes sense on numbers - Apple iOS is likely to be queried much more (not least as Cisco have a pretty good knowledge base themselves, so most folks would go there first).
Anyway, worst case if someone posts up a Cisco IOS question, one of us is likely to spot it and be able to retag to [cisco-ios]
If we find many questions on both sides, we can always come back and revisit the decision.
It would be nice if someone with the edit tag-wikis ability could also fill in the tag wikis for the ios entries with something appropriate. For those that know they're there, they can help eliminate confusion. You could also have an 'apple-ios' tag synonym for 'ios' if that is determined to be the correct mapping.