"Starting now, if you would like to maintain your free Dyn account, you must log into your account once a month. Failure to do so will result in expiration and loss of your hostname. This activity helps us eliminate hostnames that are no longer needed and/or dormant. Note that using an update client will no longer suffice for this monthly login."
We understand that the possibility of resulting service interruptions may be frustrating, so we are offering a transition upgrade offer to VIP status (Dyn Pro) for just $10 USD for the first year. Under this status, login will not be required and service will remain uninterrupted for an entire year."
It's pretty clear they are attempting to weed out the last of their free users. Are there any good free dynamic DNS services anymore?