Can't say I consider that a bad thing. This is supposed to be friends and family. You shouldn't be sharing this stuff with people you wouldn't trust with your account info.
Nope, the email gets sent AFTER you log in. Logging in is required.
After reading the FAQ I'm not sure where you're getting your statements or whether I'm confusing the points behind them?
A friend can request a share for a game already installed in his computer. My question here would rather be whether he can send a request if the game is not installed on his computer as well. If that's the only way to allow share then I can see your point.
The user guide is pretty confusing. This is where I got it from.
"To request that another user’s installed games on your shared computer are shared with you:
If another Steam user has installed a game on your shared computer, you can log into Steam on this device using your own account and send a sharing request. To do this, visit your library, where you’ll see your friend’s installed games. Select the Play button to launch a request form. Once sent, this will send an email message to the account holder."
The user guide is poorly written. I'm surprised that they couldn't have explained it better in the amount of time they had before release. All I know for sure is that you need to log in to your account on your friends/family's computer to be able to share games with them. The beta was strictly meant for family though, I don't think they had any intention of remotely requesting/sharing libraries with friends that don't live with you.