As we see the convergence of technologies through web, I think plain text is going to play a crucial role in delivering a standard cross platform solution for communication. It has already taken the center stage in form of XML. Debate on simplicity (or human side of technology) and performance will, I think, have a positive shift towards the former (people love faster development and simpler use more these days I think.. Rubyist view)
why plain text?
The concern is there although. Concern is that in addition to being human readable, the text should be human understandable as well. Using names which are semantically correct and contextually relevant is going to act as a substantial catalyst in helping dealing with these plain text files (whether it is a database or configuration file or data-transfer format).
Being always biased towards keeping configuration and databases (good old unix way) I am going to take care of this as a specification in almost all (not everything is driven by me!) development I do. You should also do the same so that your database outlasts your application!