A huge problem for anyone operating a website is the harvesting of email addresses by spammers. I get at least sixty spam emails a day, mainly because my email address has been published openly for the past few years under every article I've written on ASPnews.com. Harvesters are automated programs that scan web pages looking for email addresses, which are then sold by the million to would-be spammers. If you publish an email address on your website, you can more or less guarantee it will get harvested, and the more popular your site is, the more frequently your addresses will get harvested.
Fortunately, there are ways of masking emails that will keep most harvesters from finding them. Although in principle harvesters could find their way around the masking, in practice most harvester authors don't bother to go the extra mile to add that capability to their programs. As long as plenty of webmasters still publish emails in plain text, it's not worth the extra effort to pick up a few extra masked emails.
All of these masking techniques work fine for HTML pages, but one gaping hole in my defensive armory that I will have to leave wide open are the various RSS feeds on the site. These necessarily include contact information, and XML parsers tend to have difficulties with encoded characters, so it's not really realistic to do anything else than leave those email addresses as easily-harvested plain text. A second line of defense is therefore necessary, by adding spam filtering at the mail server, where emails are received. I'm investigating some alternatives for adding this capability, and will report back on my findings in a later posting.