Bugmenot for a Drupal blog: would it work?

I recently had some serious spam trouble, detailed here:

You might be wondering why my blog was down all day yesterday and part of today. Well, that would be because thousands and thousands of spam comments hit my blog at once, taking down the server at Open Source Host. For several days beforehand, I'd been watching phpMyAdmin and running these commands:

DELETE FROM `comments` WHERE `subject` = 'insert spam subject here'

which would delete ~2000 comments at a time (and I did this more than once a day). Finally it was too much for the server to handle. After much discussion with Charlie about possible options, I agree that the only solution, at least for the time being, is not to allow anonymous comments. This means if you want to comment, you'll have to register here. I've got comments turned off completely now, and I'll wait a few days before turning them back on.

I've been adamant for a long time that it's best not to put up any perceived barriers to communication on my blog. People don't want to register on sites and login, even though I have to point out that logging in isn't any more trouble than leaving one's name, email, and URL every time one leaves a comment. I know that after I make this change, my number of comments will be drastically reduced. People who are just cruising by, who don't plan on commenting here long-term and don't want to make the commitment of registering with the site, won't leave comments anymore. People who comment here regularly but who don't want to register won't leave comments anymore. I worry that my blog will become more broadcast, more one-to-many. I don't want it to be that way, but it seems the alternative is no blog at all, unless I want to use a different software tool, which I don't.

So right now, much as I don't like it, I'm not allowing anonymous comments. It has already affected the number of comments I receive. What I'm wondering, though, is if I could create a multipurpose username and post the username and password for people so they wouldn't have to register, thereby eliminating the steps of registering, having the password emailed to them, going back to the site, changing the password, etc. Sort of a bugmenot for CultureCat.

What happens if, say, ten or twenty people are logged in under the same username at the same time? Would it not work? I don't want to try it until I hear from some Drupal-savvy people.

Oh, and I'm also thinking about the captcha module, but if I understand my situation correctly, it's not that the spam got through, but that the enabling of anonymous comments permitted the spambots to TRY to post comments, and THAT is what brought down the server, all the hammering by scripts. Charlie has more on my situation.

So would a multipurpose username work? It might be a stupid question, but please humor me.