Just thought I'd offer a quick response:
There are certain things to remember when considering "dirty" tricks and fighting without rules.
1. Always take a scientific approach when training and analyzing any technique.
2. Realize that your practice will never perfectly resemble the conditions of a live "on the street" scenario, and always take into account those limitations.
By taking a scientific approach, you are gathering data or using previously gathered data that fits the conditions under which a fight would occur, and making conclusions based off that to project the results for using a particular approach (technique, tactic, etc.) This means looking at statistics, forensics, case studies (anecdotal), human biology, and so on, and doing so in as unbiased of a way as possible. This is how we have our data on the "adrenaline dump" that people always talk about. There is actual evidence out there regarding adrenal stress that we can take into consideration when we evaluate our training. Same with eye gauges. We know, for example, that during the eye gauge the opponent is temporarily crippled in the sense that the opponents focus changes to removing the obstruction from the eyes, but that a determined opponent can continue to fight without much hinderence once the obstruction is removed, even with slightly bothered or impaired vision. Although conclusions are always open to debate, by using evidence, we have a logical high-ground to debate from. When we use a scientific approach, we remove many of the myths or illusions that we might have about our methods.
Then, of course, we take into account that the only thing that can fully replicate combat is actual combat. Not all of the conditions will be the same in a training or competitive format. But by knowing this, we can take into account those limitations. People often make mistakes here. One might think that a technique may go exactly how you imagine it in your kata. Problem is, without objective data to back up your belief, the only thing you have to go on is your imagination, which will likely fall apart if put to the ultimate test. Similarly, one may think that a fight will be exactly "like when I boxed" or exactly like "my rape prevention class against the guy in a padded suit;" then one is unpleasently suprised if, say, multiple attackers were to present themselves in a combat situation, making the real scenario suddenly unlike the conditions one is used too.
But, I think that by taking a scientific approach, and by knowing the limitations of your training, we can reasonably train for, practice, and account for "dirty tricks," as we can for any battlefield condition.
C.