Here is a try again...

I've just posted as "Scott" even though I have never signed up here as "Scott" (now I'm Greg :)

Am I a BBTeam now or what?

It seems posting as a team doesn't work, but posting as any other bogus name works... I THINK it's a bug -- can you help explain please?

It's not a bug. You can enter as Anonymous each username you want which is not registered. This is very useful if there is more than one anonymous user. But this has nothing to do with being registered and logged in.
You can recognize registered and logged in users by the text "member" under their username. If you want you can disable anonymous posts in the options.

maybe you're right -- but it's still confusing (the user may think he's just registered using the username/password he managed to enter successfully)...

No, it's not a bug, of course. You can see that under your name nothing is written - user, member, participant... You can also forbid the names you want to.

Well, I've just added this next to sign in/post message button:

If you want to post as Anonymous then leave the username and password fields blank.

You should make you forum writtable only for registered users. Then you will not have this problem.

This is not a problem at all. How people simply write as Anonimous here without any notice? :)

Of course, if the BB is only for registered users, no one anonimous will write - with or without name...

I have been searching for sites with anonymous forums...Most say you have to register... Exactly why is that?

Exactly why is that?
To prevent spamming, for example...

I would say registering an account may be required from the forums maintainer because they collect some information like emails, for example, or some other information. In other cases, like dating or meeting forums, for example, there could be a goal in contacting other forums members privately, which is impossible if they do not have a special account.

Besides that, all forums communication may be done between guest members (like miniBB offers by default). Just a simple registration is posibly bad method of preventing of spam, because it is very simple to write a program which logs in and spams like it would be a regular user. Possibly "CAPTCHA" algorithm is the most efficient nowadays against recognizing human and a bot.

I can write here if I am not a user