If you make the power to hide writeups a level power, then I can see it... and I'd also like to suggest that if you hide the writeup, it cannot be seen by anyone else.
Also, it'd be nice to have some time limit on hidden writeups, after which time it would either automatically become unhidden, get auto-nuked with an experience penalty, or something else equally drastic. (The idea would be to discourage prolonged hidden writeups.) And the Everything daily email should include a list of hidden writeups, along with their expiration dates.
If, that is, this idea gets implemented.