Systems and methodologies for implementing automation-resistant interactive computing services are provided herein. Function invocation mechanisms can be utilized as described herein to facilitate invocation and/or activation of one or more functions of an interactive service upon performance of an interaction falling within a predefined class of interaction with selected multimedia content. The described functionality invocation mechanisms can operate similarly to a traditional captcha image by requiring interaction that is easily understandable and performable by a human user but is prohibitively difficult for an automated program to carry out. Techniques such as masking relationships between user interaction and function invocation and varying elements of the selected multimedia content for respective accesses can be utilized to provide additional resistance to automation. Described invocation mechanisms can additionally be merged with advertising, which can optionally be targeted to a particular user(s).