Quick breakdown of Sum of Squares for anyone who wants to run into the tournament prepared:
Technical basics: Take the number of centers you own, square that. You square everyone's center count. All 7 squared scores are added up. Your score is your centers squared divided by everyone's summed square totals. Solos are awarded 100

.
Effectively: If you can't take and hold a dot, giving it to a small player and keeping it out of the hands of large players will increase your score. If you're 4 dots ahead of anyone else on the board, you're doing great. If you're 4 dots ahead, and everyone is still in the game, your score is getting to be huge (40+). If you and your ally have a perfect split of centers, your score wont be as big (30-40) and is capped at 50 for a 17/17 split (good, but you score 62 with the 12 in a 12/7/5/4/4/1/1 board)
My experience: This discourages two players resolving their sphere and gobbling up the rest of the board, because even if they end up with 11 centers each, they only run a score of 30-40. In that situation if you stab your ally and manage to take, say, 4 centers, you've probably doubled your score by adding only a few centers.
Timing is very important, alliance play is obviously still important in this game (IT'S DIPLOMCY), but you want to be sure you're hard to stab as the big guy, because everyone on the board has an incentive to take dots off the top player.
As the little guy, use the scoring argument to stay in a game that you would normally get eaten. The system also encourages you to play the other side of the board, try to keep as many people in the game as possible, it will help you in the long run.
You can see some examples of how games played out with this system here: http://windycityweasels.org/game-reports/wcw-2012-season
Registration is also now open for the 2012 World Dip Con in Chicago: http://windycityweasels.org/wdc