Named accounts enable users to easily remember and communicate their account information. We don't use IP addresses to browse the internet or numbers to identify our email, so why shouldn't we have human-friendly account names for our financial transactions?
Every BitShares account is assigned a globally unique name that can be selected by its creator. There are many potential uses for account names beyond simply being an alias to a set of dynamic account permissions. They can be used as user logins or mapped to domain names. These names are transferable, which means that they are valuable in their own right.
The BitShares blockchain defines a simple algorithm to determine the fee it charges to reserve a new account name. Names that contain a number, are longer than 8 characters, or contain no vowels are essentially free. Otherwise the name is priced according to its length. Delegates can propose a different fee for each length which gives BitShares the power to adapt to market demands.
Accounts can be transferred by updating the permissions used to control the account. However, the semantics of transferring an account are slightly different in the context of a web-of-trust. Users need a means to update their keys for security purposes while maintaining their standing in the web-of-trust. In other words, users must be given a way to explicitly transfer an account name to a new user while breaking any liability for how the account is used in the future.
When users transfer an account name to another user, they use a special transaction that clears all of the links in the web-of-trust. Both the buyer and the seller are protected by this fact, because simply updating the key that controls a named account does not signify a legal change in ownership.