Greed is good?

It's a very easy way to get a unit into the East. France can't break Germany from the West without English support. With an army in SIL, BOH, or TYR, you can actually make progress quite frequently. If you make it into MUN, you keep Germany to 2 builds for certain (frequently only 1), you can usually make excellent progress against him on land due to the advantageous position you find yourself in and the extra units you have compared to him.
It does help England out to have this war to the South, but if England is opening against Russia, France shouldn't have to worry about a stab from the North. It is a massively risky move that usually guarantees you an enemy, but it can pay of huge if it succeeds.

In any game where I have Germany, if I can control, Belgium, Holland, Kiel, Berlin and Sweden, at the end of 02, then France, or Italy can have Munich, because I can kick them out easily. Apart from a stalemate situation, I regard Munich as a doorway. Especially if I don't have Germany.. Eg for France if I get an army to Munich, then it's simply a way to get to Berlin, or Kiel... Or to Tyrolia or Silesia.

My comment about those sc's at the end of 02.. the one country that, if it got an army to Munich that would be a real concern is Russia, because it might be part of a pincer type attack..eg Russian fleet in Baltic Sea and a new army coming from Warsaw,