You make valid points, Tai....but at the same time those valid points are also somewhat defeatist if you really think about it. Not to sound corny or be a Lisa Simpson about things but revolutions begin with just a few people who see an issue and decide it's worth taking up a campaign aimed at fixing it. We can't just sit and do nothing.
And not buying fish from them will do nothing to stop all of the other people who do.
The thing about the changing of the information cards - well, that employee who will be made to do that is already on the clock anyway. I have watched them doing the routine maintenance, changing things, putting sale prices up, etc all the while bagging fish and who knows what else. (You know how those jobs milk every last second of your abilities and make you multitask like crazy.) So it really wouldn't cost them too much money. Besides, they are constantly sending out new cards to replace the ones that get wet and damaged anyway. The costs are pretty nill when you think about it. For a huge corporation it really isn't much money...not a lot more than a sale sign when something is on special that week.
Let's take the same economics and put it in the opposite direction - Certainly the lab costs like a dollar...but if it gets exchanged three times, the profit has already dropped from nine to six dollars. Times that by say, four hundred stores where that happens this month - that's a loss of $1200 in what should have been profits. All it would have taken is one small information card saying that the fish must be kept in at least a 40g aquarium with only other semi-aggressive mbuna to avoid that.
All the same, I'm convinced that Petsmart's profits would benefit from more intelligent store management. Here is one example - the store in Jenkintown has a betta barracks setup so that the bettas are on a nice wall display with good lighting, and constant fresh water. These happy, healthy bettas not only have less die-off, but they attract far more buyers from what I have witnessed. Compare that to all of the other stores in my area - with the bettas in cups, many of which you can't even see unless you move a whole bunch of others...looking all clampy and drab...and dying at a higher rate....well, they naturally don't sell as much. Plus the die off will add up in loss numbers. Not to mention that an employee has to sit there and change the water in every single little cup three times a week. Now there is a waste of labor.
So for an initial investment of a few hundred dollars, the sales and survival of the fish will increase, and there will be less labor cost. It will pay for itself plus profits within maybe a few weeks.
I think it makes sense. And it's only a letter. It takes three minutes. As caring aquarists, I don't think three minutes is too much trouble for us, even if it is unlikely to do any good.
After all, people still play the lottery.