[kibwen]

  > "This is the first time you are installing a package 
  > from 'smoeuser' would you like to continue?"

You don't need package namespacing for this. All package repositories already require a registered account to publish a package.

[Klathmon]

That's a good point, but honestly I wouldn't be able to tell you the account names of any of the packages i use regularly.

And unless the account name of the package maintainers is brought front-and-center, you aren't necessarily going to know it shouldn't be different until it's too late.

[kibwen]

A user doesn't need to be able to recognize the account name, that's the purpose of your aforementioned prompt. Let's consider the possible scenarios for installing "foo/bar":

  I. I've installed anything from the author "foo" before 
     on this machine, implying that I trust "foo".
    A. On a system with namespaced packages, I attempt to 
       install "fpp/bar". I've never installed anything 
       from the author "fpp" before, so I get a prompt.
    B. On a system without namespaced packages, I attempt 
       to install "bsr".
      1. If "bsr" is by an author I trust, then it will be 
         installed. This will be confusing, but is not a 
         security vulnerability. because this author is 
         already running code on my machines.
      2. If "bsr" is by an author I don't trust, then I get 
         a prompt, as in scenario I.A.
  II. I've never installed anything from the author "foo" 
      before on this machine.
    A. On a system with namespaced packages, I attempt to 
       install "fpp/bar". The system prompts me, as in 
       scenario I.A., but because I expect this prompt I 
       don't bother reading it and blindly accept it. The 
       prompt does reiterate the name of the author, but if 
       I didn't catch the typo the first time, there's 
       little chance I'll catch the typo this time. 
       Remember: the value of the prompt is not the 
       reiteration of the name, it's in its unexpected 
       nature, because research has repeatedly shown
       that users, even power users, do not bother 
       reading routine prompts (this is why, e.g., Chrome 
       no longer allows users to bypass the enormously 
       scary warning page that appears when a secure site 
       has a certificate error). My system gets owned.
    B. On a system without namespaced packages, I attempt 
       to install "bsr". The system prompts me, as in 
       scenario I.A., but because I expect this prompt I 
       don't bother reading it and blindly accept it. My 
       system gets owned.

A more complete version of the solution that you're proposing would be to have an actual implementation of a web of trust, but even that doesn't solve all the security problems inherent to package repositories.