It's important for the internet marketer to know the information about any new technology emerges. You should be able to follow, at least know it first. That would be enough. Although there are other mobile operating systems that shouldn't be ignored (Blackberry for example), there are two giants that seem most attention, of course, iPhone OS and Android OS.
Obviously the iPhone OS running on the iPhone, now on iPads. A very popular device. Although Android is not really seen its horns yet in the tablet market, it was in high place before the smartphone market.