It's a system that rewards people that stuff keywords - effectively echoing the job requirements and adding the industry's buzzwords. It's also a system that rewards people who take a shotgun approach to applications, rather than individually crafted responses.
Ripe for exploitation I'd say.
One of the main purposes of these systems is to deal with the massive amount of shotgun applications that companies are receiving. Of course, this means that more targeted applications do not receive the consideration they deserve, thereby incentivising job seekers to use a shotgun approach.
Sounds like a vicious cycle to me.
That is, are employers wanting appropriately skilled candidates, or are they wanting individuals who happen to exceptionally savvy to the flavor of 'SEO' used by headhunters? One can't assume these groups will always overlap.