Apparently the first two responders never even took the time to read the linked post on infections which are spreading on Android devices now... An increase from %1 last year and now %4 is significant.
If users such as these continue to keep their heads buried in the sand... then malware on mobile devices will simply continue to spread more and more. As these devices become more popular... the spread of malware will only increase just as we had seen on PC's in the past.
Using common sense techniques can help in some cases... but not all. In fact, when talking about an infection that spreads through email... it is more likely to actually come from someone you know than from an unknown source. What happens in these types of attacks is that someone you know, friend or family, has their computer get infected... that infection then reads the email address's of their contacts and then sends out emails to all of the contacts in the address book. One of those contacts then opens the email, believing it is safe since it is coming from someone they know, and then their computer gets infected and the process starts all over... So these types of infections spread exponentially.
Malware authors are no longer just using porn, gambling or other similar types of websites to spread... Now they actually infect common websites that many of us visit, which in turn ends up infecting our own computers and devices.
So... If you think you are safe simply because there aren't many malwares... Remember what happened ( is happening ) on the browsers on Windows... Firefox and Chrome users used to brag that they couldn't get infected... now they get infected as easily as Internet Explorer users... Mac users used to do the same... and they are still not targeted quite as much as Windows users... but they can be infected just like any operating system.
Don't be complacent or naive.... protect all of your computers and devices with whatever you think is best for you. Not only will you save yourself money from needing to get it disinfected... but you will also help slow the spread of infections to those you care about.