The preparation of this thesis has benefited from the insights of many people, but none more than my two advisors: David Goldberg and Karen Sollins. Their patience in providing guidance and feedback has been phenomenal, and their skill at pointing me towards relevant references and resources has been acute and unerring.
I would also like to thank the many people at Xerox's Palo Alto Research Center. Over my three stays there they provided a fertile and supportive environment in which to learn how to do research. Special thanks go to Peter Pirolli who helped perform the initial analysis of data from the user behavior study, and to Ron Frederick and Berry Kercheval who provided humor and UNIX wizardry when they were frequently needed.
Finally, I would like to dedicate this work to my friends and family. I stand in admiration of my parents and the wisdom, compassion, and strength they have shown in working through the trials of life. I would not have made it this far without the love and support they have given me over the years. And to Sasha, who has in many ways made my undergraduate years worth doing.