This is good news for IT departments because it means they can significantly reduce the risk of a security breach by configuring the operating system for standard users rather than administrator. Despite unpredictable and evolving attacks, companies can very easily protect themselves or at least reduce the effects of a newly discovered threat, as long as they're ok with their users not installing software or using many applications that require elevated privileges.
In total, 64 percent of all Microsoft vulnerabilities reported last year are mitigated by removing administrator rights. That number increases to 81 percent if you only consider security issues marked Critical, the highest rating Redmond gives out, and goes even higher to 87 percent if you look at just Remote Code Execution flaws. Microsoft published 74 Security Bulletins in 2009, spanning around 160 vulnerabilities (133 of those were for Microsoft operating systems). The report, linked below, has a list of all of them, which software they affect, and which ones are mitigated by removing admin rights.
Source: Arstechnica.com