Let me add my own spin to the whole idea of "saving" bettas in those tiny containers. If you walk into a pet shop and they get their money from you for that fish in the tiny container, how does it look to them? It seems to me that it is a validation for them that presenting the fish to customers in that fashion is acceptable and will result in sales. OK, so what is the next move for a business oriented fish shop? I am sure that is an easy problem for anyone to solve. The obvious answer is that they should continue to present you, the customer, with fish who are housed in the tiny cups. For me the answer is simple. I will never be tempted to "rescue" fish in tiny cups because it means the next bunch that comes into the store will be treated the same way. By buying a fish from a tiny cup, I am encouraging the shop to treat the next batch the same way.
Now lets try another approach. I walk into a store that keeps their bettas in a more humane fashion, see one I like and buy it. The message to the shop is simple, presenting fiush who are housed humanely means sales, keep doing it. On the other hand, I walk into a shop who displays their bettas in tiny cups and never buy one. The message is simple, bettas in tiny cups never seem to sell as well. Unfortunately it takes far more than just me acting this way to actually make things change. As long as you continue to "rescue' fish from unacceptable situations, they will never notice that I failed to buy the stressed betta in the tiny cup. Instead they will have the reaction that someone, who knows what individual, bought a betta that as housed in a tiny cup. Unfortunately this means, from the shop's point of view, that tiny cups are just fine. If we don't all act in much the same fashion when faced with a betta in a tiny cup, the practice will continue.