Wow, this is a surprise for me. One of my favorite blogs Lifehacker will support Facebook log-ins in the future. This makes sense, because this supports cross-pollination, and it makes life easier for the average user (Less passwords to remember!)
Openness is the hot topic right now on the web. From aggregators to portals. In fact, Yahoo and AOL are the big sites doing this (here-Yahoo Glue, and here-ebay on Yahoo, and AOL.com)