Apple is definitely not "minute" in the smartphone market, although obviously how you define the market is key.
It is an interesting thought experiment to think about what would happen if the iPhone OS did start to head up in market share (e.g. if Apple actually released iPhone minis or something of the sort). As they approached dominance, there would be a whole number of things that they all of a sudden couldn't do. Blocking Palm from iTunes, exclusive App Store, this restriction, etc. Strategically if they started to head towards large market share it might even make sense to slow it down to preserve their freedom to operate.