Is there a compelling reason to upgrade Leopard to Snow Leopard->Lion ->Mountain Lion, such as security updates that would be missed otherwise?  
If upgrading Leopard to the current OS is desirable from a security standpoint, would I need to buy Snow Leopard, and Lion in addition to Mountain Lion?
	
		
			
		
		
	
				
			If upgrading Leopard to the current OS is desirable from a security standpoint, would I need to buy Snow Leopard, and Lion in addition to Mountain Lion?