Other donors I know feel that philanthropy is a private affair, and they simply do not wish to be thought of as philanthropists. Some have grown up with the cultural or religious belief that the highest form of giving is anonymous giving. Often donors choose anonymity if they are giving a large gift to the agency where they work because they don't want to disturb their relations with other volunteers or staff. Access to information, the right kind of information at the right time, is essential for international philanthropy. By setting up a donor advised fund with a community foundation, a donor can remain generally anonymous, but still get access to project information and the philanthropic community through the foundation's staff.
Donors often hire advisors or consultants for much the same purpose.
I think the degree to which a you want to be public about your philanthropy should be informed by strategic as well as personal considerations. By strategic I mean asking yourself what kind of impact you want to make. All philanthropy is about partnership and exchange of information, which, even through the medium of advisors, requires a degree of openess with other people. That's one of the reasons we started the International Donors' Dialogue, to give donors a place where they can be relatively open about their philanthropy in order to increase their effectiveness. Donor networks like IDD help a donor cultivate partnerships and creative collaborations.