The OP mentioned that getting copies of dissertations is difficult. Let me provide some more background on the problem.
First, the copyright is not the issue so much as the language concerning copying and distribution of the dissertation.University libraries almost always have copies of dissertations (theses are different), but the lack of clear language or law regarding copies makes them extremely reluctant to copy them.
Even if they will make arrangements for duplication there are often other hurdles. Most universities use ProQuest (UMI) who microfilms and sells copies for ~$50. Unfortunately, these are extremely low quality black and white reproductions that are often unsuitable for research. Often I end up having to order a copy from ProQuest, then go back to the university and ask them to make better copies of all the images and plates.
Universities that do not use ProQuest have a large range of policies. Some will simply not make copies (Stanford). Others will make copies only after getting permission in writing from the author (University of Michigan). Still others will make copies, but only at a high cost (~$1100 in one case from a certain public university in Colorado).
Finally, there are some cases where the university will neither copy or lend a dissertation, so your only option is to travel there to read it.
Feel free to reply if you have any questions about the process as I have learned far more about it than I ever wanted to.