You already have two froms of personal wiki on Perlmonks: Your individual home node, and your scratchpad. Both accept all PerlMonks accepted tags. Both have 64kb of storage space. Both can be linked to from your personal nodelet if you wish.
I thought the idea behind a wiki was that anyone (well , that would be any registered PM user, here) could change it? That is not possible with either your personal nodelet or your scratchpad.
Now there's an idea... what if people could not only make their scratchpad public, but have the option to make it publically editable too, for a selection of users? It would be like a common scratchpad for a discussion on the Chatterbox, started by one particular user, instead of people now each using their own scratchpad.