We only support Facebook login for one reason: Convenience.
If you use your Facebook account to sign up for Cluster, you avoid having to:
1. Supply a first and last name.
2. Supply a profile picture.
3. Remember a password.
4. Remember which email address you have as the login.
5. Verify your email address so we know it's yours.
... all with one tap.
Similarly, we don't have to:
- Have to keep sending "Forgot password" emails.
- Ask you to verify your email address, and prevent some features until you do.
- Show gray circles for your avatar, if you didn't supply a photo.
Many folks don't use Facebook heavily but have a Facebook account to sign in to services like this. By default, Facebook does not let the app you're signing into make automatic posts on your Facebook account, unless the app asks for extra permissions. You're always shown exactly what permissions an app is asking for, before allowing the app to access your Facebook info.
Cluster asks for the most basic "read-only" info from your Facebook account.