It is the density of riders that dooms the Pro World Championship where as the relatively poorly attended series events do not suffer the same problem.

If you assume the pros ride at modest 25mph that means they are travelling 11.2m/sec. That means they can come out the water/start the bike within a second of each other, and whilst still being technically draft legal, they are right on top of one another.

Looking at athletes exiting the water to find the greatest density (highest number of athletes in least time) it is roughly from the 3rd athlete to the 41st athlete with times of 21:48 and 22:39. So one can assume 38 athletes start the bike within 50 seconds of each other - at roughly 1 rider a second, and at 25mph, just outside the draft legal zone.

Assuming riders chose to adhere to the "pass the whole paceline without slotting in" rule it is nearly impossible for athlete 41 to ride up to athlete 3 as he would have to overtake a 400m long paceline moving at 28mph (Clearwater speeds). I know breaks in the line occur but I believe the underlying argument is sound. If you do not come out the water at the front it is highly unlikely you could maintain the necessary jump in power to make it to the front. Then there is some kind ITU style run race at the end.

Slowtwitch posters have suggested a solution is to increase the draft zone to 20 metres which I believe would taking athletes out the draft zone entirely (reference anyone?) but this is not possible with swimmers exiting the water at their current rate, unless everyone politely waited a second for a 20 metre gap whilst mounting the bike. Therefore a solution lies in reducing the density of swimmers exiting the water by introducing a time trial start, releasing athletes at 1 or 2 min intervals - followed by the implementation and ENFORCEMENT at a 20 metre draft zone. (I don't beleive a stagger will be effective as on the narrow roads of Clearwater, a 3 person stagger will block the entire road and make overtaking impossible)

I like the suggestion made by Paul of having a prologue to establish the gaps leading into the time trial over 70.3 distance;

Prologue: start 1 min apart, big party in town on Thu nite say 400m/4000/1600m which would take you guys 15 minutes, 5 min per sport. then a TT start on Saturday morning in the reverse order of prologue finish, at 10 second intervals.

...and it would definitely make more of an exhibition of the event. Though I think hosting the bike on a crit style circuit would be good. I don't think it suits the nature of time trialing and it is more likely lead to bunching through tight streets as Bjorn points out. 

I aslo disagree that it would make the race less entertaing, if anything I would think it would make it more so. Clearwater must have been boring to watch. There was a swim, a boring bike where everyone stayed in one long line for two hrs and then a run race. I would think it would be much more exciting to watch the virtual lead chop and change, the lead actually shifting wildly through each discipline and then tracking athletes splits through the final miles to the finish time to see if the can claw back those vital few seconds.

Without a doubt, something has to be done about enforcing the no drafting rules. Athletes have shown themselves incapable of abiding by the rules and race officials are incapable of enforcing them (whether present or not). The punishment needs to fit the crime, athletes need to fear being given a penalty so they won't even consider it. But first of all the race needs to change to a workable format.