* User must be logged in to post to wall
* Display last X entries on profile
* Post/write/submit a new guestbook entry
* User can delete entries from his/her wall
* Link to "View all Entries"
* User can disable wall postings for his/her profile alltogether
Advanced features may include
* Poster mark entry as "private" (so only the person who's profile it is can see it)
* Ban certain users from posting to my wall
* Allow only people with certain "flag" in db (example "friends=1") to post / view my entries
* CAPCHA protection to post
* Log user actions. ie. Be able to show who's written in who's wall.
* Set max number of entries / user or 0 for unlimited
* Allow HTML/markup/text only
* Allow image tags / not
.... you know, that kind of stuff.
All we really need to get this off the ground is the initial set of features above. You build it, and I'll buy it.