I'm not convinced that krellin's experiences are an indication that we should lower the minimum wage. I think that, perhaps, if his experiences are representative of *all* minimum wage workers (and this has yet to be proved), then this is an argument to change it in some way. But that doesn't necessarily mean we should lower it.
I take it as given that krellin thinks that wages should be proportional to output. A particular worker will get Y amount of money for X amount of effort, and an increase in Y should beget an increase in X, or otherwise not occur at all. Here, minimum wage mandates a given Y and he is not seeing the rise in X that he expects. Thus, minimum wage workers do not deserve the amount they are paid!
There are a number of problems with this reasoning, chief among which is that money is not the only incentive that people react to, and people react individually. A work environment, relationship with colleagues, hours, tasks, etc. all contribute to how much people want to work, and how much effort they are willing to put into their job. Furthermore, because people react individually, not all these variables have the same effect on a given person.
The second problem is that, if we hold all the above non-monetary incentives equal, I think you'll find that the relationship between wages and effort is bi-directional. If a worker perceives the job (s)he is doing to be worth more than the wages (s)he is being paid, then (s)he is unlikely to put as much effort as (s)he otherwise would. Take for example mopping the floors at a fast food restaurant. If a worker is being paid $4/hour to do so, but thinks it's worth (say) $5/hour, (s)he will only put in $4/hour worth of effort. What's the point in doing all that extra if you're only going to be compensated for a given minimum level?
Now, that's obviously a work ethic problem, but let's face it: minimum wage jobs are (usually) no fun, and it's not like putting in that extra effort to mop the floors is going to make a tangible difference in anyone's life. If we let all the non-monetary incentives become variable again, then we can see a compounding effect on effort. If my boss is a jerk and I'm being underpaid, do you think I'm going to go the extra mile? Do you think I'll even go the required miles?
If, however, we raise wages to the point where the perceived value of the work and the compensation are (roughly) equal, I bet that you'll have workers doing their very best (all else being equal, of course). This is, naturally, speculation, and I could be wrong. But the fact that I can draw a different plausible conclusion from krellin's evidence means that a decrease in the minimum wage is not a necessary consequence of his anecdotal evidence.
What is not in question, though, is that if his two-meal sample is representative of the population, there is a problem with the minimum wage. But it doesn't logically follow that from a problem, we should go in a given direction.
So, krellin's experiences are not an indication that we should lower the minimum wage. The reasons for this are (a) there are non-monetary reasons that he could have received poor service, (b) if his experiences are representative of all minimum wage workers, while there is reason to believe there is a problem with the amount given in the minimum wage, we don't have any reason to move it in any given direction without further study.