most smart phones use linux or some other proprietary operating system. Writing a virus for them would be quite a feat of skill . . . and gall.
There will eventually be something to protect them, i'm sure, but most phone apps are downloaded directly from the software vendor so they should be clean.
If you download from a third party vendor or a hack site you may fall prey to a "bad app" though.
I fought this battle with T-mobile.....Come to find out somebody was using my number to send "spoofing" texts to people and it looks like you sent it with your caller id. I fought with tmobile saying somebody had hacked my blackberry and maybe I got a virus but they informed me of the latest scam of spoofing and said blackberrys cant get viruses.
When I got my phone from Alltel, I started getting spam text messages from some hotel in South Africa.
I called Alltel and since I never use text, I just had them turn off the capability.
It's worked great ever since!
Only thing I hate about cell phones is getting somebody's old number. My first one after moving back to civilization (aka out of Alaska) was apparently an old escort service. I would get calls all hours of the night.
Now I keep getting calls from collection agencies for some douchebag I have no clue who or where he is. Does this concern these people? Of course not.