Let's say you have a free site at somewhere and want a guestbook and then need another one then you would have to sign up for another bravenet account to get 2 guestbooks
You don't have to use the 2nd or 3rd accounts for hosting websites or anything but you can host up to 10 domains on one account.
Free subdomains is one per account I do believe.
But be aware that with the free subdomain they will only offer up to 5mb of space.
That's the problem: I have several websites in one account (I'm using almost 48MB); now, with that 5MB storage limit, I have to move.
I've already found new homes for some of my websites, but if it is possible (not against the rules, I mean), I would create more 1 or 2 accounts, thus I would have more 5MB in each to use. I'm new to Bravenet (coming from Geocities), and I like it.