This list of archived pages is a cross-section of the sorts of projects that some Wikipedians have found useful and interesting, and others have wanted to remove or even salt.
Most researchers to date have not discovered that they can peruse deleted revisions -- it is a difficult process, since we don't make it easy to gather that information in dumps. So very little analysis of deletion has been done. However having had one's work deleted is often part of the reason that people choose to leave the project and not return, or to encourage others to avoid it. (in the case of a crank, that might be acceptable, though there is no need even there to create lasting enmity in a reader. in the case of most contributors, it is an unnecessary cost of making deletion a big deal rather than no big deal.) –SJ+