To top it off, I believe the tee times were a whopping 12 minutes apart and the greens were holding.
For Round 4, they were alternating between 9 and 10 minute intervals. Round 3 had 12 minute intervals because they were in groups of 3.
The weather obviously played a huge factor in the weekend's tee time arrangements as it forced the use of a two-tee start. The problem with two-tee starts is that no matter how fast your first group plays, they can't make the turn before the final group off the other side has played their second shots on their first hole and they will then be held up by those players the rest of the way around.
The Masters Committee chose to play in groups of 2 for the final round off of two tees. They put 14 groups off the front and 13 off the back, although the final group off the back was a single. The first tee time was 12:30 and the last one of the front was 2:33. The last one off the back was 2:24. If we give the player in the 12:24 group 8 minutes to tee off, get to his ball and wait for the 10th green to clear before playing his second shot and clearing the landing zone, the first group of the front couldn't have teed off on #10 until 2:32 or 2 hours and 2 minutes after they started their round. Obviously there is no incentive to play any faster than that.
When the Masters has been able to go with a traditional one tee start in the third and fourth rounds, I believe they usually use 10 minute intervals. Going with the 9/10 minute intervals saved them 7 minutes in tee times over the 14 groups, but it generally means every other group is going to get to the second tee a little closer behind the group in front than usual. As that hole will have waits for groups going for the green in 2, by the time you get to the 14th group you're going to be backed up.
As Ally pointed out Bill Yates studied this and one of the main things he found was that putting tee times too close together results in slower play do to more waiting and leads to more frustration.
Had the Committee chosen to stay with groups of 3 and 12 minute intervals for the fourth round, they would have started the final group at 2:06 or 27 minutes earlier. Of course, with groups of 3, play would have been slower for each group, but it would have felt much more normal for the players than a crowded course with groups too close together. Doing this might have jeopardized the chances of finishing on Sunday because of the slower time for groups of 3, but the players would definitely have had lesser waits. Obviously it was very important to the Committee to finish on Sunday rather than drag over to a Monday finish. They were able to do that so I guess from their point of view it was a success, albeit one that came at a price of upset players and a media that doesn't understand the tradeoffs that had to occur.