HubPages doesn't discourage or encourage multiple accounts. It's up to you.
Keeping track of Hubs does get difficult once you get over 100, in my experience. However I'm not sure multiple accounts are a good idea any more, unless you have strong reasons for needing them.
In the early days, Hubpages was one huge site and no matter how many accounts you created, your Hubs were just part of that big site.
These days, HubPages is just the platform, and each of our sub-domains is like a separate website. In general, the more content a website has, the better - so it's probably better to keep all your Hubs in one account, than split them over several accounts, unless you know you'll be able to write large numbers of Hubs on each account.
Like Wry says, if you become known as a successful Hubber, there will be those who monitor what you write about and steal your ideas - so if you start getting a profile, it can be wise to start another account which the thieves know nothing about.
Some people like to keep separate accounts to keep their commercial and non-commercial topics separate.