Leaving pathos aside, the article linked asks relevant questions:
(i) Will this event, triggered it appears in part by the very attacks on Shia pilgrims including one mortar attack earlier that killed a 'mere' 7 people, tip the balance toward ever more open ethnic strife and reprisals?
(ii) Will this event damage the constitutional process and prospects (although I myself tend to view the constitution now as something of a joke, a sideshow to the underlying, slowly brewing civil war)?
(iii) A question of my own, based on what I saw on the Arab Sats: What impact on the US Occupation forces? I note the Sats carried interviews of an Iraqi General and some Shia attendees who placed some portion of the blame on US forces having blocked off a portion of the route and bridge, causing congestion. Whether this is factual, if so why, and whate role this might have played is secondary to the issue of what has long been a widespread feeling among Iraqis - that in general US forces place their well being a distant third to US forces well being. Fair or not, it is a negative image that has bred and will continue to breed resentment even among the anti-Jihadi and anti-Insurgents.

This aside, two notes from the FT article that suggest the train of civil war left the station, rounded the bend and is coming steaming back through again:

Some Shia are treating the incident as though it were an insurgent attack, with one radio commentator placing responsibility on Iraqis ''who practice terrorism those who are silent about terrorism'' an apparent reference to Sunni communities accused of harbouring guerillas.

Sunni Arab, for their part, have in recent days accused the security forces, dominated by Shia political parties, of carrying out assassinations against their co-religionists.

Hello, my 1970s Lebanon.

Further to that observation, sadly while at first light the crowd's behaviour may seem irrational and overdone, sadly the fear and possible rumour (or again, perhaps even fact) of a suidice bomber was well-founded. That is Iraq.