I don't think there's any question of that. It's going to be a battle they'll have to fight. I don't doubt it's a problem already as there have been some reports here at WebmasterWorld over some scams.
I think Android came along at the right time, and that's what's given it such a commanding lead.
Nokia seemed to be, well, asleep, and as for Microsoft, they missed the early boat and have a lot of catching up to do, imho.