While I agree that if shrimp get eaten, it's not unnatural or cruel, I think we still have an obligation to try to provide proper care to them, even if its as simple as making sure they have moss to hide in and enough food etc. They are still living creatures, and we have put them in this situation, placing them in a small tank with a potential predator.
Again, I agree that it happens, and I won't cry if my betta gobbles a shrimp, but I won't chuck shrimp in a tank not set up for them just to see what happens or for the hell of it. By that logic you could say that betta are only 7 bucks, so just chuck it in an unfiltered unheated tank and hey, if it dies, it was probably going to die in the shop anyway, right?
I can see a lot of people disagreeing with this, but I just think that if you want to get some shrimp for your tank, you need to consider the needs of the shrimp (hiding places, space, food) and not just the needs of your fish.
Also I think even if one gal was big enough, I'd let your fish get settled first.