As little as possible. Chat guests are always anonymous, but of course with SMS guests we have a phone number and IM guests have a handle. But because we are very concerned about privacy we give you tools do deal with this. We don't store transcripts unless you ask us to, and you can delete transcripts at any time. You can also anonymize chats to delete the SMS number or IM handle, so that you don't even have a record of who contacted you. It's all under your control, and there is no additional data that we have that you can't see.