When an Army is unexpectedly faced with defeat, there is always the danger of it turning into a rout, sometimes a decisive one, such as the collapse of the German armies on the Western Front in October-November 1918, or of the Army of the Republic of Vietnam in March-April 1975, when even the North Vietnamese Army's own plans expected to achieve victory sometime in 1976, only to have Saigon fall to them in April of 1975. Both the German and Vietnamese cases were instances in which a war-weary Army, ordered into a tactical retreat, suddenly collapsed in panic, desertions, and mutiny. Sometimes a collapsing army can be rallied, as with the famous "Sheridan's ride" at the US Battle of Cedar Creek in 1864, but it is not clear if Iraq has a Phil Sheridan in reserve.
The fall of Mosul has been followed by the fall of Tikrit, and there are reports of widespread desertions from the Iraqi Army, while the Islamic State in Iraq and al-Sham (ISIS) is threatening Kirkuk.
One need not be a fan of the Maliki government to realize that the fall of the northern provinces to ISIS spells danger to the unity of Iraq (not to mention to Shi‘ites, Christians, Yazidis and other minorities). ISIS has gone from being an offshoot or subsidiary of al-Qa‘ida to being a force stronger than the original ever been, controlling a broad swath of territory in both Iraq and Syria. These are very dangerous times.