humility = truth I learned it from my friends.
Inadequately identified quotes
All quotes in Wikiquote articles should be sourced; i.e., a specific published work with a specific quotee (even if it's attributed in the publication to "Anonymous" or "Unknown") must be cited. Very few theme articles have any sources for any of their quotes. This makes it virtually impossible to maintain any semblance of accuracy or quality in these articles.
In order to encourage better sourcing, I have been bold and have just removed all quotes that were attributed to unidentified people (i.e., their wiki links went to non-existent articles). While it may be possible to track down these people and/or works, find the quotes in a publication, and then cite them, no one person (or even 20 people) can be expected to do this for over 10,000 articles. Wikiquote's articles are clearer suffering from this deficiency of unsourced material with inadequate attributions. The only solution I see is to get ruthless about eliminating any quotes that have not even a minimum level of identification — some easily accessed data about who the quotee is and why they should be considered notable enough for inclusion.
At the very least, editors adding quotes should provide a link to an existing Wikiquote or Wikipedia article, or explicitly explain who the person is in the standard source line (see Wikiquote:Templates/Themes for formatting). This doesn't eliminate the need to cite a specific published source for the quote itself, but it gives other editors a fighting chance to determine notability and find such a source.