Not having an SD Card should help shore up some security issues from attackers being able to pop and replace your card to get and put items on your phone.
The current bootloaders are not secure when unlocked and rooted -- there is no password protection -- so with a removable SD Card anyone can boot into your bootloader and put code on your phone, even if you have USB Debugging deactivated. Removing the SD Card is one step towards solving this.
The next step to hardening the phone would be to provide a security check to access the bootloader. One of the reasons given as to why this hasn't happened is because the keyboard interface isn't loaded in the bootloader so you can't enter a password. However, you can navigate up and down via volume keys so you could have sequence-based passwords like Konami codes in video games.
The current bootloaders are not secure when unlocked and rooted -- there is no password protection -- so with a removable SD Card anyone can boot into your bootloader and put code on your phone, even if you have USB Debugging deactivated. Removing the SD Card is one step towards solving this.
The next step to hardening the phone would be to provide a security check to access the bootloader. One of the reasons given as to why this hasn't happened is because the keyboard interface isn't loaded in the bootloader so you can't enter a password. However, you can navigate up and down via volume keys so you could have sequence-based passwords like Konami codes in video games.