Getting back to the original question about harvesting email addresses, I will note that it turns out that most openacs pages, but not all, that show email addresses are only provided if the user logs in. The ones that that leak this info are usually a bug. (I found a lot of these in various ticket tracke bug report modules.)
That said, from time to time, I've advocated an email mangling API to be used whenever an email address is presented. It may obscure the email entirely or display it in a jpeg or display the @ as a gif or something like that when there is no user logged in, and it might present the email address as a mailto, or something different for when a user is logged in.
I am amused by how often a google search turns up results that include statements about how google should be using a frames compliant browser.
