IDG Answers is a community of experts who are passionate about technology. Ask a question or answer one below.
A big part of it is that because there is no initial application review process, it is easy for someone with ill intentions to pay $25 and post malware applications in the Android marketplace. Honestly, I think the best security practice for an Android phone is to be very selective about what applications you download. Correction - very, very, very selective.
Beyond a deep seated presumption that any application is potential malware, I run AVG Antivirus and make certain that it is up to date. I use AVG on my laptop as well, and it has worked well for me on both platforms. Plus it has the benefit of being free.