Back in 2006 I posted about RFC 3546 and how it would allow multiple HTTPS sites to share a single IP address. Since my post a lot has changed, a new RFC  was formed and all major browsers now support this technology : IE 7+ (excluding Windows XP), Firefox 2+, Chrome 5+ (excluding Windows XP), Safari 3.2.1+ (excluding Windows XP), Opera 8+. As far as servers go Apache 2.2.12+, Nginx, and lighttpd 1.4.24+ all support it. The only major missing component is IIS for hosting websites on Windows.
Analyzing my website visitors over the past month, it appears that ~9.5% use web browsers that still do not support this technology. I plan on using this technology on internal websites, but until Windows XP becomes obsolete I do not feel like it can be used for public web sites.