Unlike iPhone/iPad apps that are individually vetted by Apple, Android apps are basically unregulated, even the ones on the official Google Android Market. I'm not sure to what extent enTourage screens apps they offer via the enTourage App Store.

I don't think you have to worry about viruses in the way you have to worry about them on PCs (via email, or web pages), however, as OncTech says Android apps can do stuff that they don't advertise, such as reading other information (shared by other apps on your device) and possibly feeding them back to a server that collects the information. Which apps do this is a bit hard to know, although from time to time a site will publish a list of Android apps they've found to be doing this. There are a number of apps that you'll see being highly recommended on these forums, but I don't think any of us know for sure if these apps are completely honest or not.

If you're worried about security on your eDGe, perhaps don't store financial or other confidential information on it, or access web banking sites, for example, as this information could possibly be leaked by a bad app. Your personal schedule, or the books your reading, or your notes, or the apps you're using probably aren't of interest to hackers looking for money.

Such is my understanding, based on my experience with Android and reading of Android news since the start of the year.