MLG_Lee once told me a story that explained the philosophy behind extended series. At a Halo event, he said, one of the best teams demolished an up-and-coming team 2-0 or 3-0 in the winners' bracket. The two teams met again in the losers' bracket, and the worse team eked out a close win against the favorites. Extended series, Lee said, would have prevented that from happening.
If MLG's goal is to help shepherd the best player to victory, extended series, in some (and perhaps all) cases, do not achieve that goal. If MLG's goal is to help the better player to win just in those matches where they have already played their opponent, extended series, in some (and perhaps all) cases, do not achieve that goal. If MLG's goal isn't either of those two things, what is it?
I made an Excel workbook that simulates a major part of MLG's 2012 tournaments: an 8-player group that features double elimination and extended series. MLG's Spring, Summer, and Fall tournaments each featured these types of groups, and those groups might make a return in Columbus after the fluke formats of 2013 Winter and Spring. I ran Monte Carlo simulations (that is, simulating the group over and over again thousands of times) in this workbook.
Whether the players were close or distant in skill... whether the players were seeded by skill or randomly seeded... whether there was a single dominant player or a more even field... in all these cases, the simulations all came up with the same result: Extended series make it less, not more, likely for the better player to win the bracket.
Typically, the difference in the rate of the best player winning the bracket was 0.5% - 1.0%. Fluctuations here were, I assume, due to ELO distribution. The difference in winrate in "would the best player win in this particular matchup" tests was 0.2%-0.8%. In the second case, fluctuations came from how often an extended series match was played: If the first- and second-best players were matched up in the first round, thus guaranteeing that an extended series would be played in a losers' bracket matchup, then the difference between extended series and non-extended series formats was relatively large.
Note that this is NOT definite proof that extended series do not achieve MLG's goals in all situations. I am not going to simulate a 128-player bracket, and I didn't simulate all possible combinations of ELOs or player seeding. However, I'm not sure why things would be much different in a larger bracket, especially since most extended series in MLG events happen near the end of the bracket.
If extended series do not achieve what MLG intends them to achieve, what good are they?
You can see the excel workbook here. (Please don't look at the formula I used to pull ELOs in column B. Yes, I know I could have just used INDEX/MATCH.)
+ Show Spoiler [how the excel spreadsheet works] +
Player ELOs are input. Players play winners' bracket matches, and match results are recorded in the table at the top right. Later, in losers' bracket matches, it is determined whether an extended match is appropriate (cell A65, for example, serves this purpose) and, if an extended series needs to be played, an initial score for the match is called. This pattern continues to the grand finals, where MLG's weird grand finals format is appropriately simulated.