I study two economic responses to the challenges of copyright infringements and spam brought about by the birth of the Internet. These responses are anti-spam mechanisms and open contents. I derive conditions under which distribution and care level taken to avoid damages in open contents are socially efficient or inefficient. Then I report experimental results on the production of open contents. I compare free- riding, efficiency and spillover when there are large or small teams using non-modular or modular production. Lastly, I propose and evaluate an anti-spam mechanism called uncensored communication channel, with the aim of enticing spam-demanders and spam-suppliers to trade in there instead of the traditional email channels. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]