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As an intermediary improves trust between two sides of its market to facilitate matching and transactions, it faces an increased risk of disintermediation: with sufficient trust, the two sides may circumvent the intermediary to avoid the intermediary's fees. We investigate the relationship between increased trust and disintermediation by leveraging a randomized control trial on a major online freelance marketplace. Our results show that enhanced trust increases the chance for high-quality freelancers to be hired. When the trust level is sufficiently high, however, it also increases disintermediation, which offsets the revenue gains from the increase in the hiring of high-quality freelancers. We also identify heterogeneity across clients and freelancers in their tendencies to disintermediate.

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Online advertising, also known as web advertising or Internet marketing, is the means and process of promoting products and services on the Internet, and it has been one of the important business models for the Internet. Due to its lucrative nature and its large scale of adoption, it has also been a target for malicious parties with various attack aims such as getting a cut of online advertising revenues, obtaining a user's privacy, and spreading malware. Over the years, a great deal of research has been conducted on online advertising. Recently, the health of the online advertising ecosystem has become more of a concern for both advertisers and regular Internet users. Advertising budgets have been abused, and Internet users' privacy and security have been infringed. In this article, we broadly study threats to online advertising and trace the root causes from a systems point of view. Existing threat mitigation strategies are also reviewed and analyzed. To protect online advertising, which has been an essential funding source of many free Internet services, several challenges still need to be addressed, including the need for transparency of the advertising ecosystem and software vulnerabilities on the client-side. To overcome these challenges, we conclude by brainstorming some innovative ideas on some potentially interesting and useful research directions. CCS Concepts: • Security and privacy → Web application security; Domain-specific security and privacy architectures;

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Although the task of data record extraction from Web pages has been studied extensively, yet it fails to handle many pages due to their complexity in format or layout. In this paper, we propose a unified method to tackle this task by addressing several key issues in a uniform manner. A new search structure, named as Record Segmentation Tree (RST), is designed, and several efficient search pruning strategies on the RST structure are proposed to identify the records in a given Web page. Another characteristic of our method which is significantly different from previous works is that it can effectively handle complicated and challenging data record regions. It is achieved by generating subtree groups dynamically from the RST structure during the search process. Furthermore, instead of using string edit distance or tree edit distance, we propose a token-based edit distance which takes each DOM node as a basic unit in the cost calculation. Extensive experiments are conducted on four data sets, including flat, nested, and intertwine records. The experimental results demonstrate that our method achieves higher accuracy compared with three state-of-the-art methods.

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