Senh: Their revenue is not where it should be. Social networks are hot right now. It might cool off in another two years. There's no guarantee they can improve their revenue by then.
I just started noticing this recently. It’s a nice touch. Before, you would have to go into a specific comment moderation page to keep track of comments. Now, it’s all tied into your profile page, just like when someone likes or comments on your status updates.
Months ago, I converted my commenting system to Facebook’s. I had my reservations before. Most of it is that because it’s javascript based, the comments will not be crawled by Google. All Google sees is the javascript code, not the actual comments.