When an application performs a rename, the *INTENT* is to insert a write barrier for the data blocks of the file involved. When is this interpretation ever wrong? When is it ever useful to be able to tell the system to replace a files contents and its name, except when the system crashes, in which case you just want its name and some garbage? Nobody ever wants that.
one very good example of when you would want to do a rename, but don't need to do a write barrier is when you are rolling logs.
this is usually done where one program has the file open and is writing data to it, another program renames the file, and then tells the first program to close the file and re-open the original name.
there is no need for a write barrier anywhere in this case.
laptop mode explicitly breaks normal expected (failsafe) behavior in the interest of of saving power. if the distro turns it on by default and never tells the user they are doing so (along with allowing the user to specify the 'how much data am I willing to loose' parameter) the distro is at fault, but that can be fixed.
adding the ability to selectivly mask this, so that you can have some programs (say your word processor) go ahead and wake up the drive to save it's data, but keep other non-critical things from doing so (even if those things _think_ that they are critical) would be a very good thing.