There's a thread on this in Sirlin.net too and I think one of guy pointed out that this isn't some kind of 8 man Street Fighter tournament where you're trying to decide who is the best Street Fighter player in the world and you don't really care about what others think about the result.
Changing the structure is impractical. Round robin tournaments have been used consistently for just about any sport and they more or less work. The last year's NBA. The Heat was 2nd seed and obviously heavily favored, so people would like to avoid the 7th seat position even if it means dropping to the 8th seat. Teams do manuever for position but the length of the NBA season makes it pretty hard/dangerous to try to purposely drop from 7th to 8th when you can just shoot for 6th instead (better position than 8th, presumably), or lose so much that you fall out of 8th completely. While tanking games, teams also just put the bench players which you can at least argue on injury issues, and even backup NBA players generally provide a good performance. There was a game where the T-Wolves had Mark Madsen shoot like 5 3s in a minute in order to lose a 5 point lead with 1 minute left in a clear effort to tank. That was noted by the NBA and while I don't think any action occurred, that only happened once and games are rarely this egregious.
Now having more games in the pool play would make it harder to tank but obviously you don't have that much time in certain tournaments. Starting all the games at the same time would help, except the Olympics is about money so it'd be pretty hard to follow it if every game started at exactly at the same time because then you can only see one game at a given time period and that's it. You can talk about some weird stuff like reseed after each round or have winner pick their opponent or whatever but someone will almost certainly figure out a way to abuse that too. Heck, China is accused of match fixing when the tournament structure is supposedly rigid. If they can pick their own opponents they would either never play their own teams, or always play their own teams and just have one team forfeit immediately if it's advantageous to do so, and nobody wants to see fixed game like that even if it gives you the best opportunity to win.
Another key point is that all the players were warned they could be DQed for continuing to throw the match based on the 'not playing at your best' clause. That is, "not playing your best" is a rule that can DQ you the game. Therefore if you're playing to win, you'd obviously want to avoid getting DQ from the tournament. Since the players ignored the warning for DQ, they were obviously not trying to win as they ultimately all got DQed. And no just the fact that 'not playing your best' is subjective doesn't matter. It's a rule and you agree to subject yourself to some judge who will decide what's 'not playing your best', and in this case virtually any observer agreed these guys aren't 'playing their best'. It's not any different than say in soccer you agree to whatever the ref decides even if there is no apparent reason for the foul he's calling. Everyone knows this rule and you've to win within what seems to be not only subjective but often impenetrable ruling. For example you'll see the host for Olympics in soccer usually get further than they ought to based on their historical strength because they get bailed out on bogus calls from refs (I rememeber South Korea won in OT in World Cup even though the opposing team scored first but the ref waved it off and there was no apparent reason why that goal was not allowed). People accept that the host/home court team in soccer has an advantage in what's obviously a subjective field (objectively you shouldn't just get favorable calls on your home turf, a foul is a foul at home or at the road) and they play within rules. You agree to the subjective opinion of a judge because he's presumably an expert and in this case pretty much everyone can agree that none of these teams were 'playing to the best their ability'.