While I expect that the amount of malware will increasingly target smart phones their design is better than Windows PCs in that apps are always compartmentalized by default, the system is easily updated and it is very simple (At least in iOS, I assume Android as well) to simply re-flash to a clean version of all your apps and OS. Compare this to what's involved in rebuilding a PC.
The iOS store isn't 100% proof against a bad app sneaking through, but it's certainly more than what you currently have on a PC where people generally google up something and install it without really being sure where it's from or what it's actually doing. (Not to mention the rampant illegal software/video which is probably the primary source of trojan infection)
Guidance from people who make their living selling security solutions should always be taken with a grain of salt.