an annoying thing about HTTPS is that it requires you to serve each domain name from a separate IP address, and that can be somewhat costly.
Also, I talked to GlobalSign recently, and they had a brand new solution that used SNI with an automatic fallback to multi-domain certificate for browsers that don't support SNI.
[1] https://code.google.com/p/chromium/issues/detail?id=43142
[2] http://en.wikipedia.org/wiki/Server_Name_Indication#Browsers...
FTFY.