What are the advantages and disadvantages for a country to join NATO?

Many countries have joined NATO because it means that they are given the full spectrum of military protection on Air, Ground and Sea aswell as all the individually specialised units for each situation and hence do not have to pay to maintain their entire military. For instance a country may join NATO, it does not then need to worry as much about an air attack as it can request another countries istance in repelling that attack and so only has to pay for a small air force or could not have any air force at all if it wishes and instead train another aspect of its military, say its infantry regiments, and offer them for NATOs use instead. Of course it also means that you are expected to go to war to protect the other members, but due to NATOs size this attack is incredibly unlikely and so this is not too big a disadvantage (unless one member decides to repeatedly invade other countries and drag you in with them........whichever member that may be)