Despite the failures and frustrations that have dogged MLS product developments for the past quarter century, end users still call for MLS capabilities. This is because the problem remains: the defense community needs to share information at multiple security levels. Most of the community solves the problem by working on multilevel data in a system high environment and dealing with downgrading problems on a piecemeal basis. While this solves the problem in some situations, it isn't practical others, like sensor to shooter applications.
The classic strategies intended to yield MLS products failed in several ways. First, the government's promotion of product evaluations failed when vendors found that MLS capabilities did not significantly increase product sales. The concept of deploying a provably secure system failed twice: first, when vendors found how expensive and uncertain evaluations could be, especially at the highest levels, and second, when security experts discovered how intractable the covert channel problem could be. Finally, the few MLS products that did make their way to market languished when end users realized how narrowly the products solved their security and sharing problems. The principal successes in MLS today are based on guard and trusted server products.