From my past experience, shoutboxes usually lead to a massive amount of spam from users. Even if you did disable the hyperlinks and spam filters, there are some who would constantly try to use that as a form of advertising. One solution to this would be to allow usage of the shoutbox after having X amount of posts to prevent newcomers from registering, only utilizing that as a means of entrepreneurship.

In my opinion, yes I love the idea of a shout box, but with everything involved and with this community's marketplace being the center point of freelance interaction for the most part, I wouldn't implement it.