Multiple blogs

I have just read a post on multiple blogs in forum section How-To and Troubleshooting. I have replied there too… but perhaps this is the right section. Multiple blogs seems to be not a feature of current WordPress release but a planned feature for WordPress 1.3. So I re-post here my opinion. I think that there shouldn’t be need for multiple prefixes to have multiple blogs running on same WordPress database instance. Taking a look to the structure of WordPress 1.2 database I have seen that there is a field called blog_id on wp_options table. The existence of such field made me think time ago WordPress 1.2 was just running as a multiblog platform. It seems I was wrong… But why using multiple prefixes? I think should be better have such blog_id field in almost all tables of wp database so posts will be categorized even according to blog_id, categories and links too, etc… Then when the structure of the database allows to categorize multiple blogs with the same database instance, should be sufficient to put in the config file of each blog its blog_id value.