I've had several requests over the last few weeks to open up the IMAPClient Trac instance so that anyone can submit tickets. Initially I changed access levels so that anoymous users could create tickets. This turned out to be fairly inflexible: it doesn't allow people to add attachments or modify tickets later. This approach also resulted in one strange ticket being created where all fields were filled with random characters - a bot looking for buffer overruns?
Since then, I've disabled anonymous ticket creation and have set up the fantastic AccountManagerPlugin which allows people to register accounts for themselves. Once someone has created an account and logged in they can create and modify tickets. I have a feeling I'm going to have to turn on the optional CAPTCHA support, but I'm willing to see how it goes for a while first.