Critical thing for the enterprise that will keep it out is running unsigned code from anywhere, and plenty of malware making it into the google app store.
Google's automated malware scanning only picks up 25% of malware apparently.
Yeah I hear this a lot. I don't know what the stats are. But I use Android daily and I haven't had any issues. I have a feeling it's similar to using a pc.... like you're probably ok most of the time but if you go the seedier places of the internet you're gonna get a bug. Some of the apps in the google store are so obviously spam/malware that if you download them you deserve whatever comes your way.