Okay, I have a(nother) really dumb question:

Do I need to be concerned about any sort of malware when I download an app? I've found some interesting apps, but I have no way of validating their safety. Has anyone used places like appbrain.com, andolib.com, appstorehq.com? The only ones I've seen posted here are slideme.org and andappstore.com. Any information would be much appreciated, and, again, I apologize for my naivete!