Android - Is an antivirus really needed for Android?
You shouldn't need to worry about running an anti-virus on your phone. I would recommend running one on your PC though and having it set to scan peripheral devices. When you plug in your phone and it gets mounted as a mass storage device the desktop's antivirus will scan the phone for viruses' signatures and you will be doing the minimum to ensure your security.
It is an illusion to believe that just because you are running *nix or OSX you won't benefit from the security afforded by AV software; that said you dont need to spend anything to get a good, lean program especially in Linux.
There have been a few reports of Trojans that basically pretend to do something, but they are actually texting short codes charing you money or stealing data or something. However, I'm not sure how these 'anti virus' programs could actually counter that as they don't have anyway to monitor what these other apps are actually doing.
All you really need to do is take a close look at the permissions requested when you install an app, and ask yourself 'should this app need full internet access and contacts access and location?'
I say no, and I have two reasons for that:
Always read the required permissions before installing any application, and ensure that this application needs these permissions for its function and not just asks to do some crap on your phone. Do not allow any application to take permission to tamper with your phone information.
Installing an anti-virus app will slow down your phone, so better scan for viruses from your PC.