I'm surprised by Eliezer's stance. At the very least, it seems the pain endured by the frogs is terrible, no? For just one reference on the subject, see, e.g., KL Machin, "Amphibian pain and analgesia," Journal of Zoo and Wildlife Medicine, 1999.

Rain, your dilemma reminds me of my own struggles regarding saving worms in the rain. While stepping on individual worms to put them out of their misery is arguably not the most efficient means to prevent worm suffering, as a practical matter, I think it's probably an activity worth doing, because it builds the psychological habit of exerting effort to break from one's routine of personal comfort and self-maintenance in order to reduce the pain of other creatures. It's easy to say, "Oh, that's not the most cost-effective use of my time," but it can become too easy to say that all the time to the extent that one never ends up doing anything. Once you start doing something to help, and get in the habit of expending some effort to reduce suffering, it may actually be easier psychologically to take the efficiency of your work to the next level. ("If saving worms is good, then working toward technology to help all kinds of suffering wild animals is even better. So let me do that instead.")

The above point applies primarily to those who find themselves devoting less effort to charitable projects than they could. For people who already come close to burning themselves out by their dedication to efficient causes, taking on additional burdens to reduce just a bit more suffering is probably not a good idea.