1. A personal data propagation service computing system configured to facilitate propagation of personal data, comprising: a memory; and a personal data propagation service module stored on the memory and configured, when executed, to: associate a personal data subscriber module with a personal data subscription data structure including indicators of a plurality of personal data items and entitling the personal data subscriber module to access the plurality of personal data items stored on a secure data store communicatively coupled to a personal data manager module, wherein the plurality of personal data items stored on the secure data store represent personal information about a user, and wherein the personal data subscription data structure includes an indication of a category of personal data items, the category indicating at least one of address information, credit card information, and bank account information; provide the personal data subscriber module to a first computing system, the personal data subscriber module configured, when executed on the first computing system, to: receive, from the personal data manager module, personal data in accordance with the personal data subscription data structure associated with the personal data subscriber module; and initiate an electronic transaction based on the received personal data; store an association of an identifier of the first computing system with the personal data subscription data structure; and provide the personal data manager module to a second computing system, the personal data manager module configured, when executed on the second computing system, to: receive from a user a specification of a maximum amount of time during which local determinations may be made before current subscription information should be obtained from the personal data propagation service computing system; receive from the personal data subscriber module a request for the personal data; determine whether the request for the personal data is in accord with the personal data subscription data structure associated with the personal data subscriber module based upon an indication received from the personal data propagation service computing system that the requested personal data includes one or more of the plurality of personal data items to which the personal data subscription data structure entitles access, wherein the determination is made locally by the personal data manager module without an intervening interaction with the personal data propagation service computing system when the specified maximum amount of time has not expired and wherein the determination is otherwise made in cooperation with the personal data propagation service module; and transmit the requested personal data to the personal data subscriber module when the request for the personal data is determined to be in accord with the personal data subscription data structure associated with the personal data subscriber module as determined in cooperation with the personal data propagation service module, wherein the second computing system is a personal computing device of the user and the requested personal data represents personal information about the user, and wherein the personal data propagation service computing system, the first computing system, and the second computing system are distinct and remote from one another.