Basically, neither Rogaine nor Finasteride have been approved for frontal baldness because in the thousands of hours of required clinical trials for FDA approval, the effectiveness was not significant enough in frontal baldnes. Of course, you have to consider that many of the men they tested on were mostly advanced "crown baldness" types, and it is generally known that nothing on this earth will save frontal hairline follicles after they have been dead over a year or so.
So basically, there is not enough clinical evidence for anyone to correctly say that finasteride or rogaine are effective in treating a receding hairline, but many physicians continue to give prescriptions for these drugs for just such use. This is because of all the anecdotal evidence and short-handed, case-study type rumors that a propecia/rogaine regemin can work. I think that it is financially unnecessary for Merck (I think it's merck, right?) to spend all that money to run the tests for frontal baldness when they can sell just as much of the drug while docs prescribe off-label.
Me, personally, I am using both Rogaine and Proscar(cut into fractions, IT IS the exact same as Propecia), and just hoping for the best. I'll try to keep everyone informed.