'Problems for the server', in this case, is as follows:
It's easy to forget, but each age represents a new world, and thus a new worldfile. The need to generate hundreds of ages for the rarest symbols means that even one person using Mystcraft can become very difficult to manage without 'pruning' unused ages; the worldfiles take up a huge amount of space.
(There's also the unfortunate conflict currently between Mystcraft and Twilight Forest.)