[EwanToo]

I've been running Android since 2.3, I've not installed a malicious app yet (to my knowledge of course).

If you want, you can install security tools which scan apps prior to being installed, like Lookout, which will alert you to various issues.

Yes there's a lot of spammy apps, but if you're even halfway aware of what you're doing, you'll have to be very unlucky to be caught out by one.