Each adoption is unique and needs to be designed to meet the specific needs and desires of the people involved. So long as the best interest of the child is the most important goal, the birth and adoptive families are free to design an adoption plan that allows complete confidentiality, or continued communication by telephone or mail, or direct contact over future years with all family members continuing to play a role in the child's life.
It is best to talk to families who have completed both open and closed adoptions to get their insight before making a decision. It is also very valuable to hear from older adoptees about their experiences and desires as well as to meet and listen to birth parents. One place to get a lot of information on open adoption is Insight: Open Adoption Resources and Support