We have two kinds of forms. One "Contact-Us" form with a mandatory message field (free text filed where leads can detail what they want) and one "Download form" with an optional message field. My sales organisation only have capacity to address the "Contact-Us" requests and the "Downloads" with a message.
In the pop-up list were I assign account managers, I would like to be able to also choose "Nobody" this is for me to know that I have taken care of that particular form submission and taken the conscious decision not to follow up. Sure, I could have assigned the lead to me as well, but I don't want to spam my own activity list.