From 12th November 2004, a new transfer of registrar policy comes into effect for all gTLDs (generic Top Level Domain - com, net, org, biz etc). The existing procedure has been refined in order to make transfers between registrars smoother. Note - this has no bearing on the ownership of a domain name.
The fundamental rule is that the gaining registrar is responsible for obtaining express authorisation from the registrant (owner) for the transfer of a domain. As previously, the losing registrar will still be permitted to notify the registrant about a transfer request but they will no longer be allowed to reject a transfer on the basis that the registrant did not respond to their notice.
These changes should actually make the transfer process easier for the customer, whilst placing the responsibility for good practice on the gaining registrar. It was generally felt that some losing registrars often used the authorisation process to block the move of their customer to a competitor, citing security as justification. This only highlights the importance of always dealing with an ICANN-accredited registrar.