I've noticed that some pastes on codepad.org include confidentiality notices in their copyright boilerplate. You own (or your employer owns) the copyright on code you paste on codepad.org, but it is a public forum! Pasted code appears on the "Recent Pastes" page, for example, where anyone can see it, and search engines can index it.
It makes sense that some people might want to use the site without revealing their code to the public, though. To support that kind of usage, I've made it possible to flag a paste as private, so that it won't be publicly linked on the site, and will include a noindex meta tag to advise search engines not to index it. Just in case, I went and flagged all the pastes in the database that included the words "confidential" or "copyright" as private pastes.
While I was at it, I added a similar feature for codepad projects. Now you can set up a private codepad project to collaborate on code that you'd rather not show the whole world.
Since paste URLs are randomly generated, they shouldn't be vulnerable to the kind of URL-guessing attacks SmugMug had problems with earlier this year. Still, these measures aren't really good enough for protecting important trade secrets — especially for projects, where the name might be guessable. If it seems like there's demand for it, I'll consider adding access control lists in the future.