For those who don't know, with the majors, and a lot of other golf tournaments on the PGA and European tours, the first-two rounds have groups of three players and the groups tee off at 11 minute intervals. In the 3rd and 4th rounds players play in pairs and at 10 minute intervals. This can change subject to weather conditions, reduced daylight times, etc.
Now, these tee-times are extremely tightly regimented. For example, at the British Open, Ivor Robson can penalise a player 2 strokes if they are 2 minutes late and disqualify them if they are 5 minutes late. That's certainly an incentive to be on time.
I'm not exactly sure as to when 11 minutes was set as the de facto for tee-time intervals, but it is one that the golf associations deem the optimum time to get every player out on the course.
Also, with an average round of golf taking a little over 4 hours, the tee-times are arranged so that, once the last groups have started, the 1st tee starters and the 10th tee starters should be nicely "in sync" on the whole course.
However, to prevent bottlenecks the following is done:
Altogether, the 11 minute intervals, the size of the groups, the encouragement of quicker play and the splitting of the rounds, are what the associations believe to be the best way of preventing bottlenecks occurring.
That said, players do sometimes catch the group before them. Only yesterday, on the first day of the 2012 US Open, Woods, Mickelson and Watson had to wait over 15 minutes for the 7th green to clear. (Live blog, 15:27).
In summary, the golf associations use their best judgement based on historical evidence whilst encouraging quick play.