Hmm - I would still recommend making `-i` mandatory. As you mention above most of our users download the `.pem` file and it is in `~/Downloads` or something like that. Now if they fail to give a `-i` flag, things will fail with some cryptic error message that might be hard to debug. The trade-off of letting power-users (or users who use keys from `~/.ssh`) not provide this flag seems less important to me.