Malware is much less of an issue for smartphones than for traditional PCs. Software downloads come from various App Stores and while some of those apps have malicious code, most of those are not particularly popular and don't show up on most searches. It's not easy to install a malicious app by mistake.
On the other hand the mobile browser presents some new security issues. Space is a premium on a small screen and often information about the security of a site, like a picture of a lock, are often not presented. A user may be more likely to click on a malicious link because of lack of appropriate indicators on the page.