Websites are, inherently, a very public thing. Anyone in the world (barring local filtering) can see your website. It’s enough to make many queasy thinking about people on the other side of the world having access to their phone number or, brace yourself, their email address.
Exposing your email address on a website does open you up to spam emails, but these days, many businesses have catchall email addresses anyway. If you have a catchall email address, the “I don’t want to get spam email” argument is already invalid.
Personally, I’m a bit of an on-line privacy nut. And with that said, hiding your business address and phone number has never made sense to me, since anyone can find the information on any number of government and yellow-pages-type sites.
If it’s on your business card, put it on your website, and make it easy to find. If your address, email, and phone number are not on your business card, it might be time to redesign those as well.
Hiding your business’s information usually only hides it from the people you want to have it: your website’s legitimate visitors. Not to mention that it leaves the impression that you have something besides your address to hide.