According to an article at PlanSponsor.com summarizing the
Deloitte 401(k) Benchmarking Survey: 2008 Edition, "motivated by fear of a dwindling workforce and concerns about employee retirement readiness, 401(k) plan sponsors are 'diligently seeking better ways to leverage their investment in 401(k) plans to attract, motivate, and retain workers.' The survey also provides plan sponsors' top indicators of successful 401(k) plans. "The top indicator of a plan's 'success' in the eyes of plan sponsors is participation rates."
Full article.