Lets face it, best practices are really someone's good idea that worked very well in a specific set of circumstances. How do you know if your circumstances are the same as those in which that good idea was implemented? Of course not, best practices do not come with a set of instructions to tell the user that they are best implemented here. My concern is that companies and individuals get careless, relying on the "best practices" to be a panacea for their troubles. Which leads me to my second point.
Best practices stiffle innovation. Best practices is all about looking back, seeing what worked elsewhere and then (often blindly) adopting it. Employees need to be encouraged to seek out solutions that fit the problem and the specific conditions that exist, and not take something that worked well elsewhere and try to force fit it as a solution. More often than not, they do not know what the exact circumstances were that allowed that solution to work well.