Changes as standards are settled may affect submission and future access. Immediate access can give competitive colleagues an edge. This can be overcome to some degree by delayed access. This varies from journal to journal and discipline to discipline, and is in a great state of flux at this time. We believe this will not be an issue for electronic dissertations in the long run, but at present this is uncertain.
Electronic publishing can interfere with publication of a whole thesis as a book.
Some publishing houses will not consider works that have appeared in any form on the web, even if it might undergo substantial revision before book publication. Copyright issues about web-published material are not well understood. Plagiarism on the Internet is a growing concern. Ethically it is important to properly cite such work. Talk to the publisher and understand their policies first, get an agreement in writing.