The cost to have someone fix absolute/non-absolute href links will far exceed the cost of SSL or an extra IP. So expect to see a broken landscape of websites post implementation.
Non-ssl rendering of local hrefs is lenient. Browsers don't complain. With forced ssl, however, badly constructed hrefs will force the browser to complain that a SSL enabled website has non-ssl hrefs.
Most people don't understand that a href needs to be absolute or how to easily fix it.
